pdf version of the entry Reductionism in Biology http://plato.stanford.edu/archives/sum2012/entries/reduction-biology/ Reductionism in Biology from the Summer 2012 Edition of the First published Tue May 27, 2008; substantive revision Mon Apr 30, 2012
Stanford Encyclopedia Reductionism encompasses a set of ontological, epistemological, and methodological claims about the relations between different scientific of Philosophy domains. The basic question of reduction is whether the properties, concepts, explanations, or methods from one scientific domain (typically at higher levels of organization) can be deduced from or explained by the properties, concepts, explanations, or methods from another domain of science (typically one about lower levels of organization). Reduction is
Edward N. Zalta Uri Nodelman Colin Allen John Perry germane to a variety of issues in philosophy of science, including the Principal Editor Senior Editor Associate Editor Faculty Sponsor structure of scientific theories, the relations between different scientific Editorial Board disciplines, the nature of explanation, the diversity of methodology, and http://plato.stanford.edu/board.html the very idea of theoretical progress, as well as to numerous topics in Library of Congress Catalog Data metaphysics and philosophy of mind, such as emergence, mereology, and ISSN: 1095-5054 supervenience. Notice: This PDF version was distributed by request to mem- In recent philosophy of biology (1970s to the 1990s), the primary debate bers of the Friends of the SEP Society and by courtesy to SEP content contributors. It is solely for their fair use. Unauthorized about reduction has focused on the question of whether and in what sense distribution is prohibited. To learn how to join the Friends of the classical genetics can be reduced to molecular biology. Although other SEP Society and obtain authorized PDF versions of SEP entries, strands of discussion have been present (e.g., whether evolutionary theory please visit https://leibniz.stanford.edu/friends/ . is inherently anti-reductionist because of the principle of natural selection), philosophical debate about reduction has shifted over the past Stanford Encyclopedia of Philosophy decade to include a wide variety of domains (e.g., development, ecology, Copyright c 2011 by the publisher
The Metaphysics Research Lab evolution, cell biology, and neuroscience), and to address additional Center for the Study of Language and Information questions about the nature and status of interdisciplinarity, such as the Stanford University, Stanford, CA 94305 integration of data or standards across biological fields. Philosophical Reductionism in Biology Copyright c 2012 by the authors interest about reduction in biology is pervasive throughout the history of
Ingo Brigandt and Alan Love philosophy and science. Many contemporary debates have historical All rights reserved. analogues, reflecting long-standing controversies among biologists about Copyright policy: https://leibniz.stanford.edu/friends/info/copyright/ the legitimacy of reductionist research strategies and modes of
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explanation used by different life science subdisciplines. relations are quite prevalent).
1. Introduction (i) Ontological reduction is the idea that each particular biological system 2. Historical Background: Philosophical and Scientific (e.g., an organism) is constituted by nothing but molecules and their 3. Models of (Epistemic) Reduction interactions. In metaphysics this idea is often called physicalism (or 3.1 Theory Reduction materialism), which assumes in a biological context that (a) biological 3.2 Explanatory Reduction properties supervene on physical properties (i.e., no difference in a 4. Problems with Reductionism biological property without a difference in some underlying physical 4.1 Context-Dependence of Molecular Features (one-many) property), and (b) each particular biological process (or token) is 4.2 Multiple Realization of Higher Level Features (many-one) metaphysically identical to some particular physico-chemical process. 4.3 Representation, Temporality, and Intrinsicality This latter tenet is sometimes called token-token reduction, in contrast to 5. “Alternatives” to Reductionism: Moving Beyond Dichotomies the stronger tenet that each type of biological process is identical to a type 6. Future Prospects of physico-chemical process. Ontological reduction in this weaker sense Bibliography is a default stance nowadays among philosophers and biologists though Academic Tools the philosophical details remain controversial, such as whether there are Other Internet Resources genuinely emergent properties. Various conceptions of physicalism may Related Entries yield different implications for ontological reduction in biology (Dowell 2006). The denial of physicalism by vitalism, the doctrine that biological systems are governed by forces that are not physico-chemical, is largely 1. Introduction of historical interest. (Vitalism also admits of various conceptions, especially with respect to how non-physico-chemical forces are We reduce and reduce and reduce, but the habits of understood; see Section 2.) Some authors have argued vigorously for the anthropomorphism and metaphor are hard to kill. (Margaret significance of metaphysical concepts in the discussion of reductionism in Drabble, The Sea Lady, 146) biology (Rosenberg 1978, 1985, 1994, 2006). Reduction (reductionism) encompasses several, related philosophical (ii) Methodological reduction is the idea that biological systems are most themes. At least three core types can be distinguished: ontological, fruitfully investigated at the lowest possible level, and that experimental methodological, and epistemic (Sarkar 1992; cf. Nagel 1998). Even studies should be aimed at uncovering molecular and biochemical causes. though arguments for and against reductionism often include a A common example of this type of strategy is the decomposition of a combination of positions related to all three, these distinctions are complex system into parts (Bechtel and Richardson 1993); a biologist significant because no straightforward entailment relations obtain between might investigate the cellular parts of an organism in order to comprehend the different types of reduction (although tacit commitments about these its behavior, or investigate the biochemical components of a cell to
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understand its features. While methodological reductionism is often (Section 3.2). motivated by the presumption of ontological reduction, this procedural recommendation does not follow directly from it. In fact, unlike the idea The philosophical study of the notion and possibility of reduction links up of ontological reduction, methodological reductionism can be quite with several core issues in the philosophy of science. As reduction controversial. It has been argued that exclusively reductionistic research involves relating (broadly speaking) one “body of scientific knowledge” strategies can be systematically biased so as to overlook salient biological to another, it presupposes an account of what the relevant epistemic units features, and that for certain questions a more fruitful methodology to be related are—theories, laws, models, concepts, or disciplines—and consists in integrating the discovery of molecular causes with the how they should be understood. Since the reduction of one theory to investigation of higher level features (Wimsatt 1980).[1] another is usually presumed to mean that somehow the reducing theory explains the principles of the reduced theory, reduction is also related to (iii) Epistemic reduction is the idea that the knowledge about one the issue of scientific explanation. For example, if a more fundamental scientific domain (typically about higher level processes) can be reduced theory fully reduces another theory or even reduces several theories, to another body of scientific knowledge (typically concerning a lower and unification (of some sort) results. The situation where a historically earlier more fundamental level). While an endorsement of some form of theory is reduced to a later theory is an intuitive case in which scientific epistemic reduction can be motivated by ontological reduction combined progress might occur. Since arguments against the existence of this type with methodological reductionism (e.g., the past success of reductionistic of reduction have maintained that terms occurring in both the precursor research in biology), the possibility of epistemic reduction does not and descendant theory have different meanings (“incommensurability”), follow from the conjunction of ontological and methodological reduction. reduction also relates to the issue of the meaning of scientific terms and Indeed, debates about reduction in the philosophy of biology have conceptual change. Therefore, accounts of reduction depend on centered on this third type of reduction as the most controversial issue commitments made about other, coordinating notions and their adequacy (see Section 4). Our discussion will therefore focus primarily on issues depends in many cases on these related philosophical commitments. This related to epistemic reduction. Prior to evaluating any reduction of one has led some philosophers to pursue an account of reduction in biology body of knowledge to another, a conception of those bodies of knowledge that is as uncommitted as possible regarding the precise construal of and what it would mean for them to be “reduced” must be explicated. A general notions such as “law” and “explanation” (Sarkar 1998; cf. number of different models of reduction have been proposed. Thus, the Brigandt 2012), or to specifically highlight how a particular package of debate about reduction in biology has not only revolved around whether general notions travels together and skews our perspective on the shape of epistemic reduction is possible, but also which notion of epistemic epistemic reduction in scientific practice (Godfrey-Smith 2008). reduction adequately corresponds to actual scientific reasoning. Two basic categories can be distinguished: (a) models of theory reduction maintain In philosophy of biology, reduction involves questions about how that one theory can be logically deduced from another theory (Section different biological disciplines and theories are related, and how biology 3.1); and, (b) models of explanatory reduction focus on whether higher itself is connected to physics and chemistry (e.g., is biology autonomous, level features can be explained by representations of lower level features possessing its own theoretical principles, explanations, and methods?).
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Over the past four decades, discussion has concentrated primarily on the The debate about reduction in biology has often been phrased in terms of question of whether classical genetics can be reduced to molecular “reductionism” vs. “anti-reductionism” (or, more archaically, genetics and biochemistry. This discussion was motivated by the “mechanism” versus “organicism” or “vitalism”). However, since increasing significance of molecular biology within the life sciences, and different notions and models of reduction have been put forward, whether proceeded from previous accounts of reduction in science, such as Nagel's one takes a reductionist or anti-reductionist stance about a particular (1961) model. A less central concern has been whether evolutionary biological subdiscipline (e.g., classical genetics) actually depends on the biology and ecology are autonomous disciplines or reducible to molecular notion of “reduction” being utilized (Wimsatt 1976b, Hull 1979). biology (Beatty 1990, Brandon 1996, Dupré 1993, Rosenberg 2006). One Furthermore, the reductionism versus anti-reductionism terminology has of the key issues in evolutionary contexts is the relationship between tended to create a false dichotomy between two extreme positions: functional explanation (“teleology”) and causal-mechanistic explanation reductionism as the idea that molecular biology can in principle fully (Wouters 2005). The levels of selection debate includes questions about explain all biological facts—making higher level biological theories whether all evolutionary explanations can be cast in terms of genes and dispensable—and anti-reductionism as the idea that higher level whether selection operates primarily or exclusively on the genetic level biological fields possess explanatory principles of their own and are fully (Okasha 2006). The main debate about reduction in genetics has lost autonomous in the sense of not benefiting from molecular biology. A some intensity over the past decade as many philosophers developed a variety of middle (and orthogonal) ground exists between these extremes skeptical consensus regarding the possibility of substantive theory and has motivated many of the efforts seen in alternative research reduction (but see Waters 1990). This decline has been accompanied by programs in philosophy of science that address questions about the nature an increasing attention to models of explanatory reduction (e.g., Sarkar and status of interdisciplinarity, such as how data, standards, or 1998, Weber 2005) across a wider variety of domains in biology (e.g., explanations are integrated across biological fields (see Section 5). Given development, ecology, evolution, cell biology, and neuroscience). For that references to “reduction” in different areas of biology pick out a example, the question of whether developmental biology can be reduced variety of commitments in different contexts—making pronouncements of to developmental genetics and molecular biology has become salient due both the success and failure of “reduction” legitimate—the traditional to recent progress in developmental genetics and growing philosophical philosophical assumption that there is a unique and global feature in need interest in developmental biology (Love 2008b, Robert 2004, Rosenberg of explication appears to be problematic (Hüttemann and Love 2011).[2] 1997, 2006), Much less attention has been given by philosophers to the question of whether biology can be reduced to physics (but see Rosenberg 2. Historical Background: Philosophical and 2006). This has been an issue of concern to many biologists (e.g., Mayr Scientific 2004), both with respect to methodology (e.g., the adequacy of analyzing a system by dissecting it into component parts) and whether modes of And what, asks Ailsa at random, as she flicks through the pages of explanation from physical science are inherently inappropriate for Darwin, is morphology? Morphology is dead rabbits in formalin, biological science (Love and Hüttemann 2011). says Humphrey. (M. Drabble, The Sea Lady, 225)
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Undoubtedly, the growth and development of molecular biology over the theme of the relations between parts and wholes because Aristotle utilized past half century has made reductionism in biology a central issue (and his science of elements and their potentials (e.g., as seen in On DNA a household word). But it would be wrong to assume that the Generation and Corruption and Meteorology) to inform his description different aspects of reductionism only gain traction in the wake of the and analysis of organism components in the History of Animals and Parts molecularization of biology juxtaposed with the discussion of reduction of Animals. He treated three compositional “levels”: composition in terms from a logical empiricist perspective (see Section 3.1). Besides a of elements and their potentials; composition of uniform parts such as perennial concern with what makes life distinctive, we can distinguish at blood and bone; and, composition of non-uniform parts that include least two reductionist themes throughout history relevant to the life multiple uniform parts, such as the face or hands. The primary biological sciences and its philosophy: (1) the relation among different branches or topic here is physiology/functional anatomy but domains of knowledge and (2) the relation between parts and wholes development/reproduction is always in view and addressed directly in the (Grene and Depew 2004, Magner 1994). These two themes link up in a Generation of Animals. Claims about “potentials” are buttressed by an complex fashion with both epistemic and ontological types of reduction. account of their contributions to material properties composing uniform (Questions about methodological reduction tend to coalesce around new parts (Meteorology IV; see Lennox 2001, ch. 8; Popa 2005). Complex technologies that open up the possibility of pursuing reductionist research dispositions (e.g., the fleshy, sinuous elasticity of the esophagus) are methods, such as making observations at a lower level with microscopy.) postulated from these material substrates that have relevance to, but do Additionally, these themes arise in the context of specific domains of not determine the nature of, these organismal parts because functional enduring interest: (a) the complex relations among different animals and strictures ultimately govern them (the fleshy, sinuous elasticity of the plants in natural environments, i.e., “ecology”, (b) the integrated relations esophagus is for the sake of repeated dilation during food ingestion). An among the parts and whole of an organism, i.e., “physiology/functional esophagus outside of the purposive context of an organism will be an anatomy”, and (c) the dynamic relations among the homogeneous esophagus “in name only”. components in the early stages of an embryo that eventually beget a unified whole organism containing heterogeneous parts in appropriate The teleological emphasis in Aristotle's biology means that he is often arrangement and connection, i.e., “development/reproduction”. characterized as a kind of ontological anti-reductionist (e.g., the elemental potentials of lower levels of organization are for the sake of but do not Aristotle is the foundation for both philosophical themes pertaining to determine the uniform parts at higher levels of organization). This blends reductionism. He addressed the relationship between domains of scientific with epistemic issues related to particular domains, such as his rejection knowledge in his concepts of superordinate and subordinate sciences of Presocratic materialist (i.e., purely “mechanistic”) explanations for the (Posterior Analytics I). Each science has a distinctive subject genus, first origin of animal morphology during development. (Empedocles principles, and set of predicates that are commensurable with the subject apparently claimed that vertebrae arise during ontogeny solely as a genus (McKirahan 1978, 1992, ch. 4–5). Though the relations among consequence of a unified cylindrical column physically breaking into the sciences are systematic, they are not necessarily reductive as there is no observable iterated units of the backbone; see Parts of Animals I.1 most fundamental science. These connections are relevant to the other [640a].) But Aristotle was also attentive to issues of material composition
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and constraints arising from the nature of properties exhibited by animal their complexity in a 1665 letter to Henry Oldenburg.[3] parts, which often mark commitments to types of ontological and epistemic reduction. His concept of hypothetical necessity (Physics II; see Immanuel Kant explicitly articulated the dialectic between a teleological Cooper 1987) permitted one kind of material to be put to use in many outlook on organismal functioning (highlighting ecological relationships, different organismal parts. Galen, among many others subsequent to physiology, and development specifically) with a mechanistic Aristotle, also explored these issues, whether it be from the perspective of understanding of causation modeled on Newtonian mechanics (Critique of how material complexes generate higher level properties (Mixtures) or the Judgment, Part II; see Zuckert 2010). Kant's maintenance of this tension relations among parts and wholes in the context of a specific domain such between the reciprocal causal relations of parts in an organism as development (The Construction of the Embryo). (“teleology”) and the linear-mechanical causality justified within his critical philosophy was a way of splitting apart epistemological and At the beginnings of the early modern period, William Harvey adopted an metaphysical issues. It could be characterized as a hybrid position with Aristotelian stance in the context of both physiology and development elements of epistemic anti-reductionism (organismal processes have to be (Lennox 2006). The relation between parts and wholes in ontogeny, understood in terms of their reciprocal contribution to a systemic goal— including relevant material properties, is constantly in view (Harvey 1981 an epistemological subordination of mechanism to teleology) and [1651]). René Descartes famously disputed these claims from the ontological reductionism (all causation is ultimately linear-mechanical). perspective of the “mechanical philosophy”. His mechanistic But Kant also understood linear-mechanical causation as a category by reductionism sought to explain the movement of the heart not in terms of which the mind frames experiences of the world. Thus, his understanding its function but rather by appeal only to the matter in motion composing of metaphysics differs from the realist one underlying most contemporary the circulating blood that is heated and thus expands akin to fermentation construals of ontological reduction. His resolution of the “antinomy of (Description of the Human Body). Descartes also made unsuccessful judgment” between mechanism and teleology is subject to varying attempts at explaining embryology in terms of matter and motion alone; interpretations. In addition to this focus on the theme of reductive e.g., tissue and organ origination is accounted for via matter slowing relations between parts and wholes, Kant also addressed the theme of the down and aggregating in different regions of the embryo (Des Chene relation among different scientific domains in his discussion of sciences 2001, ch. 2; Smith 2006, Part II). Robert Boyle defended teleological having their own distinct concepts and subject matter (Critique of explanations in anatomy and physiology (specifically, the integrated Judgment, §68, 79). relations among the parts and whole of an organism) by laying out how they were compatible with and supported by mechanistic explanations Kant's work was influential among those studying biological phenomena, (Lennox 1983). Thus, he offered a version of epistemic reduction in line even if misinterpreted in various ways, and helped to set the stage for the with his conception of mechanical philosophy, which included a mixed framing of a key reductionism related question of the early 19th century: reductionist/non-reductionist methodology and concomitant reservations teleology versus mechanism (Lenoir 1982). His discussion stressed the about ontological reduction. Baruch Spinoza famously used the image of significance of methodological conclusions—it is necessary (a maxim or a worm in a bloodstream to engage the theme of part-whole relations and regulative principle) to take organisms as natural purposes if we are to
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investigate them scientifically. This encouraged speculations about new can also be found in natural history and classificatory discourse, as seen forces, akin to those found in Newtonian mechanics, which would explain in Lamarck's Zoological Philosophy (1984 [1809]), especially poignant biological phenomena mechanistically (e.g., the formative force given his materialist perspective on living beings. explaining the development of the embryo; see Look 2006, Richards 2000). The Newtonian inspiration survived, with or without Kantian In the late 19th and early 20th century the topic of development returned traces, well into the 19th century and beyond. Comparative anatomy with a vengeance in the controversy over vitalism (sometimes termed (conceptualized broadly to include functional anatomy and embryology) “organicism”). A general movement towards a more mechanistic or exploited methodological suggestions from successful physical science, as materialistic interpretation of living systems was emerging at this time when Geoffroy St. Hilaire appealed to Newton's musings that animals are (e.g., Loeb 1912; cf. Allen 1975) and disagreements about explaining governed by similar principles or laws as those found in mechanics (Le development between Wilhelm Roux and Hans Driesch loomed large Guyader 2004). More typical is Richard Owen's discussion of matter and (Maienschein 1991). But the famous example of vitalism in Driesch's its properties within living organisms, where he exhibits a clear anti- interpretation of development and the autonomy of the organism should reductionist stance and postulates something akin to emergent be seen as an issue of epistemology as much as metaphysics (Maienschein properties.[4] This perspective was shared by many comparative 2000). Instead of materialism versus vitalism (ontological reduction anatomists who used an “analysis:synthesis” style of reasoning and questions), the explanatory conflict involved the nature of differentiation worked on marine invertebrates with complex life histories (Elwick in early ontogeny and to what degree it is prespecified. The theme of 2007). In short, there was a diversity of mechanist (“reductionist”) and order and organization in living systems (especially during development) organicist (“non-reductionist”) positions with respect to ontological, pervades many writings about methodological, epistemological, and epistemic, and methodological types of reduction in the 19th century, ontological types of reductionism at this time (emphasizing both relations similar to the philosophical diversity observable today (see Sections 3 and between physics and biology and between parts and wholes). Examples 5 below). Lenoir (1982) discusses in detail various 19th century accounts include Joseph Needham's Order and Life (1936), Kurt Goldstein's The that combine reductionist and non-reductionist ideas, especially the Organism (1934/1963), E.S. Russell's The Interpretation of Development research tradition he labels “teleomechanism”. and Heredity (1930), D'Arcy Thompson's On Growth and Form (1917), Ludwig von Bertalanffy's Modern Theories of Development (1933), and A related strand regarding reductionism winds its way through J.H. Woodger's Biological Principles (1929). Philosophers of science who physiological investigations of the 19th century. Here the Cartesian have had less influence on contemporary Anglo-American philosophy mechanical-reductionistic program is rejoined with an emphasis on the were keenly aware of these discussions. For example, Ernst Cassirer animal machine (Canguilhem in Delaporte 1994, ch. 5, 8, 10, 12; (1950, Part II), starting with Kant, explored reductionist themes related to Coleman 1977, ch. 6). Methodological types of reductionism were causal explanations of development, including the debates about qualified because of their impact on experimental design despite clear mechanism and vitalism surrounding Roux and Driesch, as well as the metaphysical commitments to a form of ontological reduction (e.g., relations between physical science and biology. These topics also Bernard 1957 [1865]). But methodologically non-reductionist approaches appeared in the pages of Philosophy of Science (e.g., Lillie 1934, 1942,
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1948, Singer 1934, 1946), although not necessarily utilizing the specific molecularization of genetics was palpable in this historical period. The terminology of reduction (Byron 2007). manifold difficulties encountered in applying Nagelian theory reduction to genetics (see Section 4) has encouraged the growth of philosophy of Ernest Nagel's general treatment of reductionism in chapters 11 and 12 of biology as an independent disciplinary specialty, in part because these The Structure of Science (1961) canvassed many different aspects of these difficulties seemed to fit a problematic pattern—misconstruing biological perennial debates. Whereas the sections concerning theory reduction have reasoning with philosophical accounts of science forged on physical usually been in view (connecting with the reductionist theme of relating science examples (Hüttemann and Love 2011, Love and Hüttemann domains of knowledge), Nagel also interacted with other biological 2011). Philosophical issues in biology seemed to require distinct analyses literature dealing with claims about parts and wholes as well as that are more sensitive to empirical research in biology (Brigandt 2011). emergence, thereby addressing the second reductionist theme that has Additionally, the rise of sociobiology and gene-centered evolutionary been prominent since Aristotle (see Nagel 1961, 366ff). He highlighted explanations provoked anti-reductionist stances among biologists on the the polysemy of “wholes”, “parts”, and “sums” inherent in claims about basis of social and political commitments (e.g., Levins and Lewontin the success or failure in showing that the whole is just the sum of its parts 1985). (pp. 380ff), predictably rephrasing the discussion in epistemological rather than metaphysical terms. Additionally he treats the question of The emergence of philosophy of biology and its attention to reductionism evolutionary emergence, i.e., whether genuinely new entities arise in the in situ within different life science contexts has led many philosophers to history of our universe and life on Earth, which had particular cache at revisit the perennial aspects of reductionism seen throughout history, this time (Goudge 1961). Nagel also dealt with the aforementioned many of which were simply tangential to the controversies over theory theoretical biologists (e.g., Bertalanffy, Russell, and Woodger) on the reduction. A number of current debates are actually unconscious returns topic of hierarchical organization and reduction in living systems, to neglected issues, albeit in different ways and in different contexts. That especially as seen in ontogeny (Nagel 1961, pp. 432ff). Nagel's developmental biology has returned to the center of the discussion is not contemporaries likewise treated reductionist themes, though their work surprising because of its enduring status as a biological topic inviting has largely been overlooked (e.g., Morton Beckner's discussion of reflection on reductionist themes. The same can be said for ecology and “organization” and “levels of analysis” as methodological and explanatory functional anatomy, although they are at present more peripheral for most aspects of reduction; Beckner 1959, ch. 9). philosophers. Socially and politically tinged aspects of reductionist research in biology, such as racial categorizations based on genetic Despite Nagel's wide-ranging analysis, most subsequent philosophical profiles, also continue to provoke philosophical analyses (see Section 5). discussion about reduction has concentrated on his account of theory reduction (see Section 3.1), and whether it serves as an adequate general 3. Models of (Epistemic) Reduction characterization of reductionism for all areas of scientific inquiry.[5] The biological case that has received the most scrutiny is the relationship He was not much of a diver. He was more of a laboratory man. between classical and molecular genetics, in part because the Diving was out of fashion. … It was all DNA and genes and
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chromosomes and microbiology and eubacteria these days. Or so of theory replacement. The Kemeny-Oppenheim model concerns the all those books had taught her. (M. Drabble, The Sea Lady, 8–9) situation where the observable predictions made by TA include all observable predictions of TB (and possibly more). In this case TA can Most discussion in contemporary philosophy of science has centered on explain everything that TB explains, but TA need not encompass the the issue of epistemic reduction (rather than ontological or theoretical principles of TB (as in genuine theory reduction), which allows methodological reduction; see Hoyningen-Huene 1989). The basic idea for the possibility that TB contains inadequate theoretical notions and is that the knowledge (or other epistemic units such as concepts) pertaining replaced by TA. to one scientific domain can be reduced to another body of knowledge (or its epistemic units) has been spelled out in different ways. It is useful to Many models of theory reduction derive from the account of reduction group different approaches to reduction into two basic categories: (1) due to Ernest Nagel (1949, 1961). Working within the philosophical models of theory reduction, which maintain that a higher level theory can framework of logical empiricism, Nagel construed reduction as a logical be logically deduced from a lower level theory, and, (2) models of relation between theories, where a theory is understood as a system of explanatory reduction, which focus on whether representations of higher statements, containing laws, formulated in a first-order formal language. level features can be explained by representations of lower level features, The reducing theory TA reduces the reduced theory TB if the laws of TB typically by decomposing a higher level system into parts (Sarkar 1992). can be logically derived from TA, which Nagel called the “condition of Models of theory reduction were of primary interest in post-positivist derivability”. However, if TB contains scientific terms that do not occur in philosophy of science that emerged in the 1960s and have received the the language of the reducing theory TA (“organismal reproduction” is not most attention (Schaffner 1993). More recently, accounts of explanatory an expression of biochemistry), then derivability presupposes that the reduction have been developed to remedy the inadequacies of theory primitive expressions of TB (in particular its predicates) can be logically focused accounts, so that theory reduction has been largely displaced as related to the language of TA. Nagel made this explicit by a “condition of the central issue by competing accounts of explanatory reduction (but see connectability”: reduction presupposes that there are statements (e.g., Dizadji-Bahmani et al. 2010). conditionals) that contain expressions both from TA and TB, such that TA together with these statements entails the laws of TB. These 3.1 Theory Reduction connectability statements are often called bridge principles (or correspondence rules, or reduction functions), and different accounts of According to theory reduction, theory T reduces T (e.g., Atomic A B their nature have been put forward. Nagel rejected the idea that bridge physics reduces Biology) if T logically entails T . Given a deductive- A B principles are analytic statements but did not take a stand as to whether nomological account of explanation (Hempel and Oppenheim 1965 they are factual or conventional. Some philosophers have required that [1948]), theory reduction as deduction from theoretical principles is an bridge principles are laws (rather than accidental generalizations), instance of explanation. In particular, T logically entails and explains the A whereas others have maintained that they should express metaphysical laws of T . Compare this with the logically weaker notion of reduction B identities between entities, properties, and processes (e.g., identifying put forward by Kemeny and Oppenheim (1956), which includes instances cells with collections of molecules, in line with ontological reduction).
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Nagel himself construed reduction as an epistemic notion without —the reduction of classical genetics to biochemistry—by Kenneth ontological commitment; he did not even require that bridge statements be Schaffner (1967, 1969, 1976; see Schaffner 1993 for his mature account). biconditionals, as mere conditionals when conjoined with TA sometimes Schaffner's “General Reduction Model” addresses a key drawback of are able to logically entail TB. (The Kemeny-Oppenheim notion of Nagel's account, first noted by Feyerabend: even though the theory to be reduction / theory replacement is weaker than Nagelian reduction as it reduced may be approximately true, it may contain empirically false does not require such bridge principles connecting TA and TB.) statements, especially if it is a historical precursor of the more mature reducing theory (e.g., the inheritance “laws” of classical genetics have This account covers interlevel theory reduction. For instance, Oppenheim exceptions). If the theory to be reduced (TB) contains false statements and Putnam (1958) argued for a hierarchical or layered model of scientific then it cannot possibly be deduced from TA. For this reason, Schaffner disciplines that assumes each layer or level corresponds to a theory. Each considers instead TB*, which is a corrected version of the theory to be discipline is reducible to the theory on the next lower level, e.g., reduced in that TB* makes more adequate predictions than TB. On this sociology to organismal biology, organismal biology to molecular model, reduction occurs if TA and TB* can be related by reduction biology, molecular biology to chemistry, and chemistry to microphysics functions (bridge principles) and TB* follows logically from TA enriched (see also Walter and Eronen 2011). Another way to apply Nagel's general by the reduction functions. (While Nagel focused on the laws of TB being model is successional theory reduction, where a historically earlier theory deducible from TA, Schaffner requires that all statements of TB/TB* are is reduced to a later, more mature theory, so that reduction can be an deducible from TA.) Schaffner's central tenet about reduction in biology is instance of theoretical progress (Nickles 1973). In both cases Nagel held that the success of molecular biology shows that classical genetics and that theories needed to be indexed to a particular time: “The question traditional fields of experimental biology are in the process of being whether a given science is reducible to another cannot in the abstract be reduced to biochemistry. While this reduction has not been completed yet, usefully raised without reference to some particular stage of development a logical derivation of traditional experimental biology from a of the two disciplines” (1961, 361). In this context, reduction (and (completed) theory of biochemistry is in principle possible and will especially Nagel's connectability condition) was prominently criticized by eventually be achieved. Schaffner's account has an ontological aspect in Paul Feyerabend (1962, 1965a, 1965b) and also by Thomas Kuhn (1962). that he interprets the reduction functions as synthetic statements Feyerabend argued that an earlier and later theory may use the same expressing identities between the entities and processes of the two theoretical term with a different meaning (e.g., “mass” in classical and domains related (in line with Sklar 1967 and Causey 1972a, 1972b), relativistic mechanics). This incommensurability of meaning makes the though he does not argue that these identities are metaphysical connectability of these theories' expressions, and thus the logical necessities. The Nagel-Schaffner approach to theory reduction assumes a derivation of one theory from another, impossible. Whether or not syntactic account of theory structure such that they are axiomatized genuine incommensurability obtains is controversial (see, e.g., Sankey systems formalizable in first order predicate calculus. A variety of other 1994). models of theory reduction exist, some of which use a semantic (i.e., theories as families of models) rather than a syntactic account of scientific Nagel's model was revised and applied to a specifically biological context theories (see Woodger 1952, Suppes 1957, Hooker 1981, Balzer and
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Dawe 1986a,b). biology as the reducing theory does not consist of a small body of laws, so that a covering-law model of explanation and reduction is not Schaffner's account provided the motivation and point of departure for applicable (Culp and Kitcher 1989, Kitcher 1984, Sarkar 1998). If much of the reduction debate in philosophy of biology, which was molecular biology or other biological fields are inadequately represented conducted primarily in the 1970s and 80s and centered on the issue of as consisting of a clearly delineated theory reconstructed as a set of whether (and in which sense) classical genetics can be reduced to statements in a formal language, then an account of reduction that molecular genetics or biochemistry. Three criticisms pertaining presupposes this construal of scientific theories is problematic. The specifically to the Nagel-Schaffner model bear mentioning. (Section 4 Nagel-Schaffner account also may fail to view scientific theories as reviews the main objections to different models of reduction more dynamic entities that change over time (Hull 1976, Wimsatt 1979). generally.) (c) Hull (1976), Wimsatt (1976a, 1976b), and Sahotra Sarkar (1992, (a) Michael Ruse (1971) and David Hull (1974) have argued that the 1998) have objected that Schaffner focuses too much on formal relation between classical and molecular genetics is one of theory considerations about reduction, rather than substantive issues. His account replacement, not reduction in Schaffner's sense. Although Schaffner's construes reduction as a logical relation that is “in principle” possible account permits a correction of the theory to be reduced (TB* instead of even though it is not occurring in practice. If reduction in this sense is not TB), it is not clear when a modified version TB* (corrected “classical occurring in biology, then significant questions arise as to whether it best genetics”) still counts as being largely similar to TB (classical genetics). fits biological knowledge and practice. Nagel claimed that premature This leaves the ambiguity of whether one should conclude that TB was attempts at reduction can retard scientific progress, thus implicitly reduced because TB* is similar enough or that TB has been replaced by decoupling methodological demands from epistemological ones (Nagel another theory because the two are so dissimilar (Hull 1976, Ruse 1976). 1961, 362–3). Schaffner (1974, 1993) acknowledges that reductionism in Schaffner himself only requires that TB and TB* are “strongly analogous” his sense has been peripheral to the practice of molecular biology, but (1993, 429), without offering a specification of how much similarity is maintains that his formal model of reduction captures the reduction required for reduction rather than replacement (Winther 2009). William relation between theories. Wimsatt (1979) suggests that Nagel's and Wimsatt (1976b) emphasizes that while interlevel, compositional Schaffner's focus on in-principle considerations and the context of reductions are transitive, successional reductions through history are justification, to the exclusion of in-practice considerations and the context intransitive, so that a continuum between genuine successional reduction of discovery, leads to misunderstandings about the nature of reductionism and replacement obtains. Any sequence of successive reductions can be debates, including historical and current controversy among scientists (see expected to evolve into an instance of replacement given enough time. Section 2). Reduction may obtain between classical and molecular genetics, but not in the sense of Nagel's or Schaffner's logical empiricist (b) Nagel and Schaffner relied on a syntactic construal of theories, which approach (Hull 1974). assumes that a theory is a set of statements in a formal language, including laws (Kitcher 1984). Yet it has been argued that molecular 3.2 Explanatory Reduction
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A variety of explanatory reasoning patterns used by life scientists are now (b) A characteristic difference between theory reduction and explanatory under scrutiny in philosophy of biology and theory reduction is no longer reduction stems from the fact that the former—focusing on the epistemic the primary focus. Various models of explanatory reduction focus on notion of logical deduction—does not incorporate explicitly the reductive explanation and differ from theory reduction (which is also a historically ubiquitous ontological idea that a reduction explains the whole kind of explanation, at least on the deductive-nomological notion of in terms of its parts (see, e.g., Winther 2011). Models of explanatory explanation) in two important ways: reduction typically assume that reductive explanation is causal explanation, where a higher level feature is explained by the interaction of (a) While theory reduction assumes that reduction is a relation between constituent parts. Stuart Kauffman (1971) gave an early expression of the theories, models of explanatory reduction permit other features as the idea that the search for explanations in experimental biology proceeds by relata of a reductive explanation, such as fragments of a theory, decomposing an overall system into interacting parts. Wimsatt (1976b) generalizations of varying scope, mechanisms, and even individual facts. also recognized that this more naturally mapped onto the language of One approach pursued along these lines is due to Kenneth Waters (1990, biologists, especially the practice of discovering and elucidating 1994, 2000). Instead of construing theory relations in terms of the Nagel- mechanisms. Mechanism approaches have now developed into a robust Schaffner model, he identifies a key principle of inference operating in alternative to theory reduction (see Section 5). Given that many classical genetics and molecular genetics, the “difference making philosophers of biology and neuroscience conceive of explanation as the principle” (gene differences cause differences in phenotypes), which can description of mechanisms, accounts of explanatory reduction can rely on be ascribed to genes in both classical and molecular genetics. An the notion of a mechanistic explanation (e.g., Delehanty 2005). explanatory reduction is achieved between them because their causal roles correspond. Waters (2008) extends this account by emphasizing how the Models of explanatory reduction avoid the problems facing theory investigative practices of classical genetics were “retooled” by reduction mentioned at the end of Section 3.1. Since explanatory developments in molecular genetics, which accounts for the success of the reduction is not committed to the relata of an explanation being theories corresponding explanations. involving laws, it can defend the possibility of reduction without formally reconstructing a clearly delineated theory of molecular biology or Another example of explanatory reduction is due to Marcel Weber classical genetics. Its focus on reduction as explanation of a whole in (2005). In line with models of theory reduction, Weber maintains that the terms of its parts captures a feature of actual molecular explanations. explanans essentially involves biochemical (“physico-chemical”) laws, Whereas accounts of theory reduction have to acknowledge that reduction which carry the explanatory force. But he assumes that the explanandum in their sense has not yet been achieved and must appeal to the “in is a fact or basic generality about biological mechanisms (rather than a principle” possibility of reduction, accounts of explanatory reduction genuine law or a whole theory), such as the mechanism of action comport well with the piecemeal nature of actual scientific research. potentials in neurotransmission. By permitting the explanans to make Experimental and molecular biology can offer reductive explanations reference to higher level structures such as axons, he does not require that even if many facts have not yet been explained and existing explanations it contain exclusively biochemical expressions.
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still require more details to be filled in. Current biology effectively issues about reduction in genetics (especially representation, see Section explains individual facts and generalities of smaller scope, and the 4.3), rather than formal considerations in a theory of reduction, Sarkar explanans can be a mere fragment of a theory (see, e.g., Schaffner 2006 develops a view of explanatory reduction that is not committed to a on “patchy and fragmentary” reductions). Finally, given that mechanistic particular account of explanation. Two such basic types of reduction are explanations in experimental biology are preceded by and closely tied to “abstract hierarchical reduction” and “strong reduction” (or spatial the discovery of mechanisms, explanatory reduction provides an account hierarchical reduction), where the latter unlike the former requires that of reduction that can be related to scientific discovery, while approaches entities of a lower hierarchical level are physical parts of higher level of theory reduction have to separate the context of justification (reduction entities. (Each type of reduction can come in stronger and weaker forms and explanation) from the context of discovery. as different kinds of approximations are involved in different reductive explanations.) Sarkar argues that explanations in classical genetics, which An early model of explanatory reduction was put forward by William explain phenotypic patterns in terms of classical genes, are abstract Wimsatt (1976b). Wimsatt assumes that a reduction is a causal hierarchical reductions. The entities involved in this case are alleles, loci, explanation of an individual event (rather than a generality), involving a linkage groups, genotypes, and phenotypes, which stand in hierarchical “compositional redescription” of a higher level state of affairs into some relations (e.g., alleles A and a form genotype Aa), with individual alleles of its component features. This model is related to Wesley Salmon's occupying the lowest level. It is an abstract rather than a spatial (1971) account of statistical explanation, which uses the notion of hierarchy; the assumption that A and a map to Aa at the next higher level screening off to explicate the idea of one property being statistically more does not require Aa to be a physical entity that has A and a as its spatial relevant (and thus more explanatory) than another one. Wimsatt replaces parts. Furthermore, the genotypic entities in this hierarchy are governed Salmon's statistical relevance with the idea of causal relevance (as by various transformations and regularities (principles of inheritance), explanatory reduction in biology involves the search for causally relevant such as segregation, linkage, and mutation. Phenotypic patterns of factors), and he develops the notion of “effective screening off”. This inheritance are explained by genotypic features in the well-known fashion involves the idea that the compositional redescription and explanation in of classical genetics. While this abstract hierarchy can be interpreted as a terms of a lower level property can have a greater “cost” of explanation spatial hierarchy by viewing classical genes as being parts of (e.g., by being more complicated) than the description in terms of the chromosomes, Sarkar's point is that the various practices in classical higher level property that is effectively screened off. A consequence of genetics such as segregation and linkage analysis did not require a the epistemic “cost” requirement is that an explanatory reduction that physical interpretation of genetic maps, and that the explanations in terms effectively screens off a described higher level feature does not make it of an abstract hierarchy can be genuine reductions since they invoke a irrelevant and thus eliminable (as in Salmon's account) because it can be lower and thus more fundamental hierarchical level. retained for pragmatic purposes. Regarding spatial hierarchical reduction, Sarkar argues that this regularly Sahotra Sarkar's (1998) detailed discussion of reductionism and genetics occurs in molecular biology, where certain parts of experimental biology offers several relevant conceptual clarifications. Focusing on substantive are reduced to molecular biology, more precisely macromolecular
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physics. The various components of cells form nested part-whole (why-necessarily) by the PNS operating on the molecular level (often relations, resulting in a spatial hierarchy. Many mechanisms of classical occurring at some relatively distant point in evolutionary history).[6] genetics can be reductively explained by the physical principles governing the behavior of macromolecules (though approximations are still 4. Problems with Reductionism necessary). Explanatorily relevant principles for the physics of macromolecules include weak interactions, hydrogen bonding, You can't learn everything from the laboratory, that's what he hydrophobic bonding, allosteric transformations, lock-key fit, and the idea used to say. The whole is more than the sum of its parts, he told that structure determines function. Sarkar's central tenet is that the us. The whole behaves differently from the parts, and has different elucidation of the molecular mechanisms of replication, recombination, properties. That's what he taught us, and he was right. It's out of and cell division provide reductive explanations of the principles of fashion to say these days, when we spend our time scrutinizing the classical genetics. While classical genetics offered an account of gene interactions of eukaryotic microbes, but it's true, nevertheless. It's transmission and could also rely on cytological explanations, these still true. (M. Drabble, The Sea Lady, 140–1) accounts did not yield a complete explanation of how and why Accounts of theory reduction and explanatory reduction face several recombination occurs. Molecular biology filled in this gap and corrected potential problems. Some critiques of (epistemic) reductionism emphasize classical genetics. that the effects of molecular processes strongly depend on the context in Other models of explanatory reduction have been put forward by which they occur, so that one molecular kind can correspond to many philosophers, many with an explicit eye to capturing how reduction higher level kinds (Section 4.1). A prominent and significant challenge to occurs in scientific practice (e.g., Bickle 2003, 2006, 2008). In some ways reductionism stems from the fact that higher level biological structures the most unique defense of explanatory reduction is found in the recent and processes can be realized by different kinds of molecular processes, work of Alex Rosenberg (2006), which departs from his earlier critical so that many molecular kinds can correspond to one higher level kind focus on theory reduction (1978, 1985, 1994). Rosenberg's argument has (Section 4.2). A point that has not been stressed in previous critiques of multiple components. First, strict laws (universal, exceptionless, spatio- reduction is the fact that biological processes must be represented before temporally unrestricted) are required for explanation and the only they can be explained (Sarkar 1998). Attending explicitly to candidate law in biology is the principle of natural selection (PNS). representation highlights two features that have received less attention in Second, why-necessary explanations are better than how-possible debates about explanatory reduction: temporality and intrinsicality explanations in historical sciences such as biology, but why-necessary (Section 4.3). explanations are only available at the molecular level because structure 4.1 Context-Dependence of Molecular Features (one-many) becomes decoupled from function above this level. Therefore, all how- possible explanations in “functional biology” (i.e., non-molecular One key challenge for reduction stems from the fact that the effect of a biology), even those invoking the PNS, and any descriptions from molecular entity or mechanism may strongly depend on the context in functional biology involving higher levels of organization get explained
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which it occurs (Hull 1972, 1974, 1976; see also Wimsatt 1979, Gilbert reduction such as Nagel (1961) and Schaffner (1976) have replied that a and Sarkar 2000, Laubichler and Wagner 2001). Classical geneticists molecular reduction can take the relations of parts and the context of were fully aware of the fact that a phenotype is brought about by the molecular processes into account, e.g., by specifying the relevant context interaction of several classical genes—the same allele may lead to two as initial conditions in the molecular premises from which the higher level different phenotypes if occurring in two individuals with a different state is to be deduced (Frost-Arnold 2004). overall genotype (Waters 2004). Although one-many phenomena have been known for some time, it is now a robust empirical generalization Context-dependence is primarily a problem for models of theory that a molecular pathway may have different effects in different cellular reduction; models of explanatory reduction often take the organismal contexts, so that the same pathway can be involved in different functions context for granted without being committed to reducing it molecularly in different species or in different parts of an individual (Gilbert and (as seen in reductive explanations offered in experimental biology). Sarkar 2000, Laubichler and Wagner 2001, Burian 2004).[7] These Science can avail itself of causes as difference makers relative to a given different contexts include developmental and physiological history, which causal context (Waters 2007, Woodward 2003). Both experimental condition the behavior of molecular pathways (Brigandt 2006, Kirschner investigation and explanation can focus on one among many causes, 2005). Even the amino acid sequence produced by a molecular gene may relegating everything else to the context or background (which is often depend on DNA elements outside of this gene and non-genetic factors, so held fixed in experimental studies). For example, if the loss in function of that a gene can code for distinct products in different cells or different a particular gene leads to an abnormal phenotype in a knock-out states of a cell (Stotz 2006). Thus there is a one-many relation between experiment, this gene is one causal factor implicated in the development molecular kinds and higher level kinds: a molecular mechanism can of the normal phenotype. Explanations appealing to this gene—as a causally lead to or be part of different higher level states depending on the salient causal factor relative to a context—are genuine explanations even context.[8] if the other genes involved in the phenotype are unknown and the cellular context of the gene has not yet been understood (Waters 1994, 2007). If A common conclusion drawn from these one-many relations is that the molecular biologists discover that the same mechanism produces different parts and molecular components of an organism have to be understood in effects in distinct contexts and only one of these effects is the target of terms of the organized whole in which they occur (recall Kant's regulative inquiry, a part of the mechanism's context becomes epistemically relevant principle; Section 2). Although biologists universally view the and can be included in the explanation (Delehanty 2005). decomposition of a system into its lower-level parts as reductionistic (an instance of methodological reduction, see Section 1), they often construe In contrast, an account of theory reduction such as the Nagel-Schaffner the attempt to understand how the parts are organized so as to bring about approach is committed to deduce a description of a higher level the system-level properties as a synthetic, non-reductionistic endeavor phenomenon from purely molecular premises. In order to deduce even a (Bechtel 2010). Paying attention to context and organismal organization is single higher level statement (a fortiori a total higher level theory on a valid methodological recommendation; however, it is less clear why this Schaffner's account), the premises must contain (in addition to the lower is an argument against epistemic reduction. Proponents of theory level laws) a specification of the total lower level context—every feature
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that has some causal impact. This includes features internal to an organismal context can always be molecularly described. For example, an organism and some part of its environment. While explanatory reduction appeal to developmental genetics research success alone is inadequate for can appeal to particular causes relative to a background that is not reducing cellular context to molecular causes because the discovery of molecularly specified, a logical deduction as required by theory reduction genetic causes occurs against a fixed organismal background (Robert can go through only if the total causal context is contained in the 2004). The dependence of molecular features on a cellular and organismal premises.[9] A molecular characterization of the total context is in context poses problems for theory reduction approaches maintaining that principle possible due to ontological reduction: for any higher level state higher level phenomena can be deduced from purely molecular premises. there is always a total molecular configuration that determines this higher (It is also a problem for claims that the embryo can be computed from a level phenomenon. However, this entails a retreat to the “in principle” purely molecular specification of the fertilized egg, as endorsed by possibility of a molecular derivation because not only is the molecular Rosenberg 1997; see Keller 2002, ch. 9.) Thus, there are boundaries on specification of the total context currently unavailable but it may not be the kinds of explanatory inferences that can be drawn from reductionist forthcoming in the future (Hull 1972, 1974, 1976).[10] In this respect research strategies. What remains missing from many philosophical accounts of explanatory reduction have a clear advantage over models of discussions critical of reduction is an explicit account of methodological theory reduction, as the former are committed neither to formal derivation strategies and epistemological frameworks that both capture actual nor the assumption that the explanans of the reductive explanation scientific reasoning and offer an alternative to reductionism (Love 2006, involves only molecular notions. 2008; see Section 5).
Jason Robert's (2004) treatment of explanation and methodology in 4.2 Multiple Realization of Higher Level Features (Many-One) developmental biology highlights what is probably the main valid point stemming from the context-dependence of molecular features. While Apart from the one-many relation between molecular and higher level acknowledging the legitimacy of reductionistic research strategies that kinds, Hull (1972, 1974, 1976) also points to the existence of a many-one isolate molecular causes relative to a background that is held fixed for relation as a challenge for reductionism. This turns out to be a potential experimental purposes, Robert emphasizes that this methodology does not problem for both theory reduction and explanatory reduction (though to license an inference to an exclusively reductionistic position maintaining differing degrees). Hull's point is that the same higher level phenomenon that all explanatorily relevant causes are molecular. That developmental (e.g., a Mendelian trait such as coat color) can be produced by several genetics uncovers various differences between individuals that are due to different molecular mechanisms, or that a higher level phenomenon is differences in gene expression does not entail that genes are the only realized by different kinds of molecular configurations (multiple factors relevant in ontogeny. As genetic research holds other cellular and realization). In defense of his model of theory reduction, Schaffner (1976) organismal factors fixed, the causal influence of these non-genetic replies that it is sufficient to specify one such molecular situation. The resources is simply not assessed by this research method. It begs the higher level situation that is determined by the molecular constellation question against those who maintain that some explanations of then can be logically derived from this specification the higher level development must invoke higher level features to simply assert that the situation that is determined by the molecular constellation. However, one
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has to be clear about the nature of the explanandum in a reductive But epistemic reduction requires reducing higher level concepts and, since explanation (i.e., what is the consequent of a reductive deduction). Is it a Mendelian dominance can be brought about by different kinds of type of higher level phenomenon (described by higher level predicates) or molecular situations, this higher level predicate corresponds to many merely a token phenomenon (an instance of a higher level phenomenon)? molecular predicates, making any reductive translation of higher level Theory reduction is the idea that a whole theory (such as classical concepts very complex. (And, in addition to translating such concepts into genetics) can be reduced, or at least that its laws can be reduced. The molecular terms, theory reduction also requires deducing higher level Mendelian principle of segregation, for instance, is a law describing a generalizations involving such concepts.) A similar issue can apply to phenomenon occurring in all sexually reproducing organisms, not just a explanatory reduction. Biology attempts to explain kinds of phenomena token phenomenon, so this general principle—covering various lower occurring in different contexts and organisms, so that reductive level realizations—would have to be explained/deduced molecularly. explanations must molecularly explain kinds of phenomena in addition to single instances. Consider the example that Schaffner (1993) offers in support of the possibility of reduction: the Mendelian concept of “dominance”. On his Subsequent discussion based on ideas in metaphysics and philosophy of account, given certain classical genes a and b, the property “allele a is mind has clarified how one conception of the many-one relation between dominant (relative to allele b)” can be expressed in molecular terms as molecular and higher level kinds can bear on epistemic reduction. In his follows. Assume that genotype aa yields phenotype A and genotype bb general treatment of reduction in psychology and social science, Jerry corresponds to phenotype B, while ab yields A (because of dominance). Fodor (1974, 1975, 1997) distinguishes between token-token reduction We ascertain that gene a consists of DNA sequence α and gene b consists and type-type reduction (or between token physicalism and type physicalism). Token-token reduction is the idea that each token higher א of DNA sequence β, and that phenotype A is brought about by protein This yields the level process is metaphysically identical to a token physico-chemical .ב while phenotype B is brought about by protein following supposed reduction: process (the weak sense of ontological reduction that has nearly universal assent: see Section 1). The dispute centers on how much more than token- Allele a is dominant (relative to b) iff the presence of two copies token reduction is possible. A substantially stronger idea is that each type thus of higher level phenomenon corresponds to one type of lower level] א of DNA sequence α molecularly produces protein phenotype A], the presence of two copies of sequence β produces phenomenon. Type-type reduction yields a bold version of epistemic phenotype B], and the presence of one copy of α and reductionism, as in this case higher level concepts and knowledge about] ב protein phenotype A]. (Schaffner 1993, 442) higher level phenomena could be immediately reduced to molecular] א one copy of β produces notions. Yet Fodor argues that type-type reduction (regarding mental and While Schaffner explicitly claims to have shown that the predicate (or social kinds in particular) is empirically false. Consider a simple law or concept of) “dominance” can be reduced to the language of biochemistry, causal principle of a higher-level science relating two kinds S and T, such his evidence actually shows how a single instance of dominance (allele a as ∀x(Sx → Tx), which can be read as “all Ss are Ts” or “all events of is dominant to allele b) is brought about by states on the molecular level. type S bring about events of type T” (some laws or principles might be of
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a more complex logical form). As a matter of fact, a higher level kind is higher level phenomena in a similar way. Rosenberg's earlier discussions often realized by several different kinds on the physical level (different criticizing theory reduction in light of multiple realization (1978, 1985, instances of the higher level kind are of a different type on the molecular 1994) used Donald Davidson's (1970) notion of supervenience, which is level). If kind S is realized by the lower level kinds M1, M2, …, Mi, the another way to spell out the idea of ontological without epistemic bridge principle (reduction function) is of a disjunctive form: reduction (non-reductive physicalism). Higher level facts supervene on physical facts if any difference between two higher level situations ∀x (Sx ↔ (M x ∨ M x ∨ … ∨ M x)) 1 2 i implies a difference in the physical basis. Yet this is consistent with two distinct physical situations corresponding to the same higher level state T is likewise multiply realized, say by the molecular kinds N1, N2, …, Nj. Fodor's point is that the lower level basis of the higher level law ∀x(Sx → (many-one). Since biological properties such as fitness supervene on Tx) consists in several laws (reducing different higher level instances), physical properties, fitness can be nothing more than a combination of such as: physical properties, even though no such property complex is necessary for having a particular fitness value. Higher level theories abstract away ∀x(M1x → N3x), ∀x(M2x → N1x), ∀x(( M3x ∨ M4x) → N2x), … from irrelevant variation in lower level features and thereby arrive at generalizations that are explanatory precisely because they do not include Thus, while on the higher level there is one unified law ∀x (Sx → Tx), its features irrelevant to the phenomenon to be explained (Putnam 1975, translation into molecular terms is a disjunctive statement: Strevens 2008). From this perspective, theory reduction of classical to molecular genetics is impossible as the many–many relation between ∀x ((M1x ∨ M2x ∨ … ∨ Mix) → (N1x ∨ N2x ∨ … ∨ Njx)) classical and molecular kinds makes any reductive account radically This disjunctive statement has the appearance of being a gerrymandered disjunctive. At the same time, the notion of supervenience implies that combination of laws rather than a genuine law. Therefore, the higher level classical and molecular genetics are not incommensurable, and that law cannot be reduced to a unified lower level law. Token-token molecular genetics can shed light on the exceptions of classical genetics. reduction obtains, but since the natural kinds (to which laws apply) of the A related critique of reductionism in genetics is due to Philip Kitcher higher level science cross-cut the kinds of the lower level science, type- (1984). He argues that it is not that the complexities of any reduction (due type reduction fails and the law-based explanation on the higher level to the many-one relations between molecular and higher level kinds) cannot be replaced by a unified law-based explanation on the lower level. exceed our cognitive capacities. Rather, the reductive, molecular account Steven Kimbrough (1978) argues that this situation also applies to the does not adequately explain because it does not involve the natural kinds relation between classical and molecular genetics: ontological (token- that underlie the appropriate causal relations. Principles of classical token) reduction is possible, but not epistemic (type-type) reduction.[11] genetics (e.g., segregation) are explained by cellular processes (e.g., the The multiple realizability of higher level kinds is viewed by many as an behavior of chromosomes in meiosis) because the higher level kinds obstacle to reduction (e.g., Kincaid 1997), and a number of philosophers picked out by cytology are causally relevant. Rephrasing these cellular of biology have taken the many-one relation between molecular and processes in molecular terms leads to an account that mentions various
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disjunctive combinations of molecular kinds, while failing to exhibit the preferable relative to another epistemic quality, such as unification. And unified kinds that are the causes of the process being studied. A key unification itself can be explicated differently in terms of functional or aspect of Kitcher's argument is that an epistemic account of reduction structural features of biological systems (see, e.g., Weiskopf 2011).[12] fails for ontological reasons, by not capturing the natural kind structure of It is natural for contemporary accounts of explanatory reduction to focus chromosomal phenomena studied by classical genetics. on mechanisms and the study of model organisms. One reply to the Schaffner's reply to the multiple realization objection (1993, 463–6) holds multiple realization objection from this perspective explicitly argues for that the same DNA sequence can be present in many individuals, so it is token-token reduction, discussing how the causal description of a token not just a token phenomenon that is studied by molecular biology; mechanism explains (Delehanty 2005). Weber (2005) acknowledges that molecular generalizations apply to restricted types. This is true but fails to higher level features are multiply realizable, yet this does not hamper the address the core issue. Critics of reductionism do not argue that each reducibility of token systems or individual organisms: “the fact that higher level type corresponds to several lower level tokens (which is chemotactic behavior is multiply realizable does not affect the trivially true) or that molecular biology can study token phenomena only. reductionistic explanation of this organism's behavioral biology” (48). Rather, the point is that a higher level type corresponds to several lower However, this stratagem ignores the key point of contention because level types, and for each of these lower level kinds a distinct molecular token-token reduction is uncontroversial. It is a relatively trivial claim account obtains. Thus, a unified (as opposed to disjunctive) causal that follows from physicalism. The focus on token phenomena or explanation of the higher level phenomenon appears impossible. individual organisms fails to address an important epistemological feature of scientific knowledge: some scientific explanations pertain to a single Waters (1990) challenges the commitment to unification that implies there organism only, but (in general) explanations cover types of phenomena. is explanatory loss in appealing to the multiply realized “gory details” of In many biological contexts, such as developmental biology, the molecular biology. In some cases, disjunctive explanations at a lower intellectual aim is to explain phenomena instantiated in many organisms; level seem to explain better than unified explanations at higher levels. and the use of model organisms is predicated on this aim.[13] Any version Elliott Sober (1999) extends this line of argument: an explanation in terms of epistemic reductionism has to address this feature of scientific of higher level kinds can be more unified or general by encompassing knowledge and explanation to be adequate. Explaining development—as heterogeneous lower level kinds, but this same heterogeneity exhibits understood by many developmental biologists—means to have an account important differences in scientifically interesting properties. Only the of ontogeny exhibited by individual organisms belonging to a larger lower level science can account for such differences and therefore, in this group (e.g., understanding the developmental principles that govern sense, offers a deeper explanation than the higher level science. As a vertebrate or amphibian development). As the same morphological result, explanations are not better or worse along a one-dimensional scale, structure may develop in different species by means of different processes but there are several epistemic virtues an explanation can possess— and based on the action of different genes, multiple realization obtains and generality as well as depth. Sometimes a lower level explanation is better is relevant for such explanations (Laubichler and Wagner 2001). relative to one epistemic property, while a higher level explanation is
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Moreover, even if the aim is to explain a feature of a single organism— more robust causal connections. This is one reason why some biological the situation considered above by Weber (2005)—it does not follow that sciences preferentially invoke higher level entities and processes in the an explanation should exclusively appeal to the factors on the lowest face of multiple realization, explaining in terms of higher level natural level. An explanation should only include factors that are explanatorily kinds and causes. relevant; an irrelevant factor is one whose omission from (or modification in) the explanation does not prevent the explanandum from following In summary, the level(s) of organization a successful explanation (Strevens 2008). This also holds for mechanistic explanation, which addresses often depends on the particular explanandum. If the aim is to should cite those features as components of a mechanism whose explain a type of phenomenon, multiple realization issues (many-one) modification would make a causal difference to the explanandum may arise. In the explanation of a token phenomenon, the explanation phenomenon (Craver 2007). For instance, chromosomes are relevant parts should include lower level factors only to the extent that they are of the mechanisms needed to explain Mendelian patterns of inheritance explanatorily relevant for that particular explanandum. (Darden 2005), but this particular explanation will go through regardless 4.3 Representation, Temporality, and Intrinsicality of what the lower level, molecular composition of the chromosomes is (e.g., whether or not the various genes have similar or very different DNA Sarkar's (1998) account of explanatory reduction draws attention to the sequences). requirement of representation: natural phenomena must be symbolized, embodied, pictured, or designated through media such as equations, scale In the context of developmental biology, even during the development of miniatures, or abstract diagrams. Every reductive explanation in science a single organism, a structure may be present across time and have a involves a representation of the systems or domains to be related by stable developmental-functional role, yet its underlying molecular and reduction. (Note that this is not the question of how theory structure is cellular basis may change (Brigandt 2006, Kirschner 2005). Entities above represented; see, e.g., Schaffner 1996.) Almost all of the discussion the molecular level can be more robust so that when some developmental surrounding one-many (Section 4.1) and many-one problems (Section processes change or break down these higher level entities are not 4.2) for theory and explanatory reduction assume or presume particular modified or removed. Knocking out a gene need not have any impact on representations that directly impact the arguments offered (e.g., they ontogeny due to genetic redundancy, while eliminating a particular cell or involve approximations of different kinds). Sarkar distinguishes three group of cells may dramatically interfere with normal development representational criteria for a reductive explanation: (i) fundamentalism: (Brigandt 2012, Mitchell 2009). A higher level causal connection can be the explanation of the phenomena relies entirely on features that pertain more salient in that the regular operation of the mechanism strongly to a more fundamental realm; (ii) abstract hierarchy: the system is depends on the presence of this kind of causal relation. This is not to deny represented as a hierarchy, where the lower levels are regarded as the that such a higher level cause is realized by molecular entities and their more fundamental; and, (iii) spatial hierarchy: the abstract hierarchy is interactions (i.e., supervenience obtains). But if a higher level process is rendered physical by the requirement that the entities on the lower level less sensitive to disturbance or intervention than certain molecular causes, are (spatial) parts of the entities at the higher levels (see Section 3.2). the more powerful mechanistic explanation can be the one that appeals to
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Whether or not there are one-many or many-one relations between (Hüttemann and Love 2011). In most discussions of epistemic reduction, different hierarchical levels turns on the nature of the hierarchy invoked both theoretical and explanatory, no explicit distinction has been drawn and how it is characterized. The decomposition of a system is not a between constitutional or spatial relations (arrangements) and causal or univocal enterprise and, depending on the principles utilized, can generate temporal relations (dynamics; but see Mitchell 2009). One source of the both competing and complementary sets of part representations from the focus on spatial relations is the objection to reductionism from structural same system (Kauffman 1971, Wimsatt 1974, Craver 2009). Certain organization (Polanyi 1968; cf. Delehanty 2005, Frost-Arnold 2004, governing principles are often visible, such as functional versus structural Schaffner 1993, ch. 9.2), which is related to the “context” objection decompositions (Bechtel and Richardson 1993, Winther 2006). Therefore, (Section 4.1). Moreover, physical science models used as a template for prior to determinations of whether reductive explanations succeed or fail, thinking about reduction emphasize spatial composition questions rather questions of representational choice and adequacy need to be explicitly than causal relations (Love and Hüttemann 2011). As Schaffner has addressed. remarked: “Biological theories are usually given in the form of a series of temporal (and frequently causal) models. In physics, time is usually These representation issues are not idle with respect to differing eliminated by making it implicit in differential equations, whereas in explanations, both past and present, because the same line of argument biology a temporal process … is the rule” (1993, 83–4; cf. Kellert 1993, about the non-independence of organismal parts constituted reasons for 93). Nagel presciently recognized differences between spatial and treating the organism from a non-reductionist standpoint (Aristotle, Parts temporal reasoning in his discussion of teleological explanation (in part of Animals II.3; Owen, Hunterian Lectures [1837] in Sloan 1992, 213–4). because he was reading the literature on explaining ontogeny by Individuation of parts and their explanatory relationship to wholes is theoretical biologists; see Section 2). critically dependent on the principles utilized in representing them (Love 2012). Wimsatt (1974, 1986, 1997, 2007) has claimed that reduction and The contrast between structure and function is evidently a contrast emergence are compatible within the context of explaining organizational between the spatial organization of anatomically distinguishable complexity in living systems, going so far as to argue that reductionist parts of an organ and the temporal (or spatiotemporal) methodology can identify emergence when specific conditions of organization of changes in those parts. What is investigated under aggregativity are delineated. Different failures of aggregativity result each term of the contrasting pair is a mode of organization or a when different conditions are not met, leading to a subtle taxonomy of type of order. In the one case the organization is primarily if not compositional relations, as well as highlighting that different exclusively a spatial one, and the object of the investigation is to decompositions yield distinct fulfillments and/or violations of those ascertain the spatial distribution of organic parts and the modes of conditions that can be methodologically exploited by scientists for the their linkage. In the other case the organization has a temporal purpose of causal discovery. dimension, and the aim of the inquiry is to discover sequential and simultaneous orders of change in the spatially ordered and linked In addition to individuation, two other issues directly related to parts of organic bodies. (Nagel 1961, 426) representation can be mentioned: temporality and intrinsicality
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Kitcher also glimpsed the potential significance of temporality for (Dupré 1993, 94–5) reductive explanation in the context of embryology: “Because developmental processes are complex and because changes in the timing What this distinction misses is the possibility of diachronic aspects of of embryological events may produce a cascade of effects at several part-whole or interlevel relations. Scientific explanations commonly different levels, one sometimes uses descriptions at higher levels to invoke dynamic (causal) processes involving entities on several levels of explain what goes on [later] at a more fundamental level” (1984, 371). organization (Craver and Bechtel 2007). This is one of the core reasons why development is a persisting biological topic for reductionism. During A very different distinction utilizing time, which is agreed upon by ontogeny there are causal interactions over time among parts and diverse participants, has arisen to distinguish between the historical activities (both homogeneous and heterogeneous) to bring about new succession of theories via reduction (“diachronic reduction”) and current parts and activities (both homogeneous and heterogeneous), eventually attempts to relate parts to wholes, such as in explanatory reduction or generating an integrated adult (whole) organism. interlevel theory reduction (“synchronic reduction”; see Section 3.1). Temporality can be added as a fourth criterion on representations for Synchronic reduction is mereological explanation, in which the reductive explanations: (iv) temporal hierarchy: for an abstract hierarchy behavior of more composite items described in reduced theories is embedded in an explanation, the entities and their behaviors on the lower explained by derivation from the behavior of their components by level are temporally prior to the entities and their behaviors at the higher the reducing theory. Thus, reduction is a form of explanation. levels (Hüttemann and Love 2011). Although temporal or process Diachronic reduction usually involves the succession of more hierarchies have not received the same attention as spatial hierarchies general theories which reduce less general ones, by showing them (such as in Wimsatt's aggregativity criteria), their importance is seen in to be special cases which neglect some variables, fail to measure explanations that invoke higher level features (e.g., tissue interactions coefficients, or set parameters at restricted values. As the history during ontogeny) at an earlier time to causally explain lower level of science proceeds from the less general theory to the more features at a later time (e.g., gene expression patterns). For example, a general, the mechanism of progress is the reduction of theories. study of the developmental origin of aortic arch asymmetry involves a (Rosenberg 2006, 28) mixture of reductionist and non-reductionist representations according to the criterion of temporality (Yashiro et al. 2007). The explanation depicts The first distinction to note is that between synchronic and several events in a sequential process. First, fundamental level properties diachronic conceptions of reductionism. The term reduction is (gene expression) change non-fundamental level properties (arterial often used to refer to the relation between a theory and its structure), which alters blood flow dynamics (thereby fulfilling the historical successor. … This is … what I mean by diachronic temporality condition). These new dynamics induce a subsequent change reductionism. My concern, on the other hand, is solely with in gene expression (thereby violating the temporality condition). This synchronic reductionism, that is to say, with the relations between altered gene expression then produces the non-fundamental property of coexisting theories addressed to different levels of organization. interest, aortic arch asymmetry (thereby fulfilling the temporality
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condition). Thus, depending on how time is represented and which in reductive explanations. Wimsatt (1980) drew attention to the fact that temporal partitions are utilized, an explanation may be reductive, non- every investigation must divide a system from its environment and that reductive, or both. This is a good example of how ontological and methodological reductionism favors attributions of causal responsibility to epistemic reduction can yield strikingly different answers. A biologist “internal” parts of a system rather than those deemed external (see also using a higher level feature at an earlier time to explain a lower level Wilson 2004). In the protein folding case it appears that the failure of feature at a later time (a non-reductionist explanation by the criterion of temporally indexed explanatory reduction involves causal powers of temporality) is not denying that this higher level feature is composed of something extrinsic to (an instance of) the process under scrutiny (i.e., the lower level features (e.g., cells and molecules), nor the possibility that the folding of a single amino acid chain). The presumption of atemporal, higher level feature was caused by a different set of lower level features compositional relationships has encouraged this distinction to be ignored at some more distal point in time. because nested part-whole relations are predicated on a prior individuation of a system from its environment (Hüttemann and Love Another example is found in protein folding within molecular biology 2011, Love and Hüttemann 2011). This line of thought relates to the (Hüttemann and Love 2011, Love and Hüttemann 2011). Functional context-dependency objection (Section 4.1) but emphasizes the proteins are folded structures composed of amino acid components linked importance of functional dependency relations uncovered by attending to together into a linear chain. If we ask whether the folded protein is temporality in addition to structural organization. mereologically composed of its amino acid parts given current representations in molecular biology, then the affirmative answer seems Recognizing temporal aspects of reductive explanations found in biology to favor explanatory reduction with respect to the spatial hierarchy. But if alongside other representational issues like intrinsicality, which are not we ask whether the linear amino acid chain folds into a functional protein captured by a focus on mereology alone, supplements the evidential base (a causal process with a temporal dimension) purely as consequence of its for an argument in favor of talking about different kinds of reductionism linked amino acid parts, then the answer is less clear. Empirical studies rather than in terms of a unified account of reduction or overarching have emphasized the necessary role of other folded proteins to assist in dichotomies of “reductionism” versus “anti-reductionism” (or “holism”). the proper folding of newly generated linear amino acid chains (Frydman Once we incorporate distinctions regarding different types of reduction 2001). That the linked amino acid components alone are insufficient (ontological, epistemological, and methodological), the different causally, even if they are sufficient constitutionally, allows for a more interpretations of these types (e.g., theoretical versus explanatory explicit appreciation of the significance of temporality and dynamics epistemological reductions), the different representational features (Mitchell 2009), especially because the relations of interest concern only involved (spatial, temporal, etc.), and the distinct biological topics to molecular biological phenomena (as opposed to higher levels of which philosophers have applied them (e.g., development or functional organization, such as cells or anatomy). anatomy), it is more difficult to conceptualize a single, adequate conception of reduction that will do justice to the diversity of phenomena A final representational feature is intrinsicality, i.e., how what is and reasoning practices in the life sciences. The multiplicity and “internal” and what is “external” are explicitly or implicitly distinguished heterogeneity of biological subdisciplines only reinforces this argument
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and suggests to some that we should move beyond reductionism entirely. with the concept of an inter-field theory (Darden and Maull 1977, Maull 1977). For example, the advent of the chromosome theory of inheritance 5. “Alternatives” to Reductionism: Moving Beyond in the 1910s bridged the previously unrelated fields of Mendelian genetics Dichotomies (which studied phenotypic patterns of inheritance across generations) and cytology (which dealt with the material contents of cells). This interfield The brutality and the reductionism of the microbiological victory theory effected a unification of these two fields but Mendelian genetics had not destroyed all speculation. Ethology and ethologists had and cytology were not reduced to each other, nor did the interfield theory been savaged, but they had not perished. (M. Drabble, The Sea reduce both fields. More recent work has articulated interfield relations Lady, 150) without relying on the notion of a theory (Bechtel 1986, Burian 1993, Grantham 2004a, 2004b, Mitchell 2002). This parallels the trend in Much of the past discussion about reduction presupposes a unitary view models of explanatory reduction of moving away from theories as the of the scientific enterprise that involves a close relation between natural only epistemic units of interest (Section 3.2), but the emphasis is on relata kinds, laws, counterfactual dependence, explanation, and confirmation such as coordination, integration, synthesis, or reciprocal interaction. A (Godfrey-Smith 2008). One of the ubiquitous features of modern biology rationale for these relata emerges from the demand for multidisciplinary that seems prima facie incompatible with many methodological and research; the explanatory task involves coordinating diverse epistemic epistemological reductionist theses is the proliferation and flourishing of resources, which amounts to an implicit rejection of the “fundamentality” diverse biological subdisciplines, molecular and otherwise. Despite the of one particular discipline producing the most empirically adequate purported “hegemony of molecular biology” (Kitcher 1999a), biological explanations. subdisciplines focused on higher levels of organization have not disappeared. As Fodor (1997) has felicitously put it: “Special sciences: In this context, Alan Love (2005, 2008) uses the notion of a problem still autonomous after all these years”. For some time this feature of agenda to argue that some scientific problems not only motivate biological research, along with many of the problems associated with interdisciplinary research but also provide structure for the requisite theoretical reduction (especially its inapplicability to scientific practice, intellectual coordination (see also Brigandt 2010, 2012, Brigandt and but also the difficulties in identifying clear-cut and distinct “levels” to Love 2010). Problem agendas consist of numerous component questions reductively relate), have prompted philosophers to reject “reduction” as that stand in systematic relations and are tied to associated standards of the appropriate (or only) relation among concepts and explanations from explanatory adequacy. These standards imply what epistemic resources different domains.[14] Instead, relations of coordination driven by a and different disciplines are needed to address the problem. The relations commitment to unifying, integrating, or synthesizing aspects of scientific among component questions of the problem agenda (i.e., its internal knowledge have been offered (Bechtel and Hamilton 2007, Potochnik structure) foreshadow how various contributions can be coordinated to 2011). generate an adequate explanatory framework. Building on this perspective, Ingo Brigandt (2010) suggests that there is no single, linear Lindley Darden and Nancy Maull were at the forefront of this discussion hierarchy among scientific fields (e.g., Oppenheim and Putnam 1958), but
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that the relationships among theories and disciplinary approaches are entities: classical genetics focuses on meiosis and involves chromosomal determined by and vary with the scientific problem being addressed. behavior; molecular genetics focuses on gene expression and involves These philosophical accounts align with general research on various molecular entities such as nucleotide sequences. Relations interdisciplinarity, which has identified the presence and articulation of a between the two fields are manifested as differential attention to distinct complex question as a prerequisite (Repko 2008, Szostak 2002, 2009). aspects of a larger, temporally extended mechanism. Thus, instead of unification being a regulative ideal with biologists seeking as much unity as possible in their explanations of the complex The mechanisms framework has proved particularly fruitful in capturing natural world (e.g., Kitcher 1999b), an erotetic perspective suggests that explanations that appeal to entities at several levels of organization. An particular problems determine the need for and degree of any integration instructive example is Carl Craver's (2005, 2007) discussion of multilevel (Brigandt 2010). William Bechtel's (1993, 2006) studies of cell biology and multifield explanation in the context of neuroscientific studies of document how the formation of new subdisciplines generates both learning. While the cellular-molecular process of long-term potentiation is integration among approaches and some disintegration due to new critical for memory formation, it is not merely a molecular counterpart of specializations. Bechtel's attention to the institutional underpinnings of memory. Long-term potentiation is a lower-level component of an biology also meshes with sociological analyses of disciplinary overall, multilevel mechanism. Reductionist accounts have neglected the organization (Gerson 1998). phenomenon of disciplinary integration at the same level of structural organization and invested too heavily in finished reductive explanations, Recently, accounts of explanation revolving around “mechanisms” have ignoring the dynamic changes in research strategy that precede them been widely discussed (e.g., Bechtel 2006, 2008, Bechtel and (Craver 2005). In addition to searching for molecular correlates of higher- Abrahamsen 2005, Craver 2006, 2007, Darden 2006, Glennan 1996, level phenomena (downward-looking episodes), there also have been Machamer et al. 2000). Many philosophers view experimental biology as attempts to understand the role of molecular mechanisms in complex fundamentally concerned with the discovery of mechanisms (Darden and higher-level phenomena (upward-looking periods of research). Craver 2002, Tabery 2004), where mechanisms are understood as akin Sometimes progress has been achieved independently of or by (though not equivalent) to machines with interconnected, organized parts abandoning reduction as an explanatory goal. This need to change operating to produce regular or expected outcomes. Conceiving of strategies depending on the research context is ubiquitous in mechanistic biological explanation in terms of mechanisms provides a philosophical research (Bechtel 2010), which serves as another reminder for framework that closely tracks biological practice and does not rely on the philosophers to attend to actual scientific practice. Even though a notion of a theory. Besides providing new models for explanatory mechanism is temporally extended, philosophical analyses of mechanisms reduction (Section 3.2), mechanisms also have been used to demonstrate may not capture all aspects of temporality (see Section 4.3). While integration among different fields. Darden (2005) argues that both discussions have focused on the representation of time relative to a reduction and replacement fail to capture the relations between classical mechanism (e.g., Bechtel 2006, Machamer et al. 2000), not all aspects of and molecular genetics. Both fields deal with different mechanisms that the dynamics of biological systems are well represented as mechanisms occur at different periods of the cell cycle and involve different working involving entities and activities. Some might be better modeled using
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equations (Bechtel and Abrahamsen 2010, 2011, Weber 2008), and in The philosophical import of biological complexity is underscored by other cases time might be represented independently of the mechanisms recent trends in systems biology (Boogerd et al. 2007, Noble 2006, being investigated.[15] O'Malley and Soyer 2012). In addition to the mathematical modeling of Complexity also has been a source for the articulation of non- system-wide behavior, systems biology has a wealth of data about various reductionistic epistemological accounts of biological reasoning (Wimsatt molecular components of cells stemming from functional genomics, 1974, Hooker 2011). Sandra Mitchell (2003, 2009) has argued that RNomics, proteomics, and metabolomics methods. Downward looking different forms of biological complexity block standard reductionist strategies in systems biology attempt to break down systemic dynamics perspectives. Multiple (idealized) causal models must be integrated from into different components, whereas upward looking strategies aim to different disciplinary approaches to adequately represent this complexity, understand how the quantitative interactions among individual molecules including our uncertainty in predicting its behavior, which has result in higher-level behavior (Krohs and Callebaut 2007). Despite the implications for any social policy derived from these models. She focus on molecular components and their interactions, non-reductionist specifically draws attention to the phenomenon of self-organization, themes tied to complexity are motivated by non-linear interactions and which refers to how system behaviors or patterns emerge from non- feedback loops that generate emergent behaviors, distributed control, and specific interactions among lower-level components (Camazine et al. system robustness (Bruggeman et al. 2002, Westerhoff and Kell 2007). 2001, Kauffman 1993), such as the collective behavior of social insects. Another distinct strand of discussion about reductionism is found in (Self-organizing phenomena are also relevant to reductionism in physical critical analyses of methodology and explanation from the perspective of science; see, e.g., Goldenfeld and Kadanoff 1999, Whitesides and feminist philosophy of science and studies of the social aspects of science Ismagilov 1999.) Although decomposing a system into parts is important (e.g., Fehr 2004, Longino 1990, 1996). Feminist philosophy of biology for claims about self-organization, there is no localization of causal has related reductionism and pluralism to other philosophical, scientific, responsibility to these components (Bechtel and Richardson 1993, ch. 9). and social issues. One core idea in these discussions is that forms of Instead the system behavior is a function of generic patterns of component reductionism are involved in mutually reinforcing feedback loops with interaction, which foregrounds how complexity emerges from dynamics other factors, e.g., socioeconomic status or expectations about gender rather than constitution (see Section 4.3). For example, gene networks and (Keller and Longino 1996, Levins and Lewontin 1985). Thus, human social networks may exhibit isomorphic patterns of self- reductionism, whether ontological, epistemic, or methodological, can be organization due to their interactive structure, which is unrelated to understood as a manifestation of more diverse commitments (e.g., whether genes or humans are the components. Thus, self-organizing political ideology) than much of the philosophy of biology literature on phenomena occupy a odd place in the reductionism discussion because reductionism would suggest—the history of biology points in this components are used to explain the behavior of the system but it is the direction as well (see, e.g., Allchin 2008). This line of criticism also nature of their interactions (not their specific characteristics) that generate suggests that the interrelations between reductionism in biology and the patterns of behavior, which are often referred to as emergent properties of social sciences should be treated more explicitly. Elisabeth Lloyd (2002) the system (see also Grantham 2007).
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has argued that medical research should not be restricted simply to reduction. But it is an open question whether they supplant discussions of molecular biological investigation because higher levels of social reduction or bear some complex relation to them (Craver 2005). Reasons organization that are culturally sanctioned have unrecognized causal in favor of the latter position include the continued use of “reductionist” effects on health. As the social sciences and medicine attempt to apply language (for and against) in biological research, as well as the fact that a different life science reasoning strategies, similar philosophical issues near universal reason for rejecting reduction and choosing an alternative predictably transfer, but with the potential for more socially damaging is the problematic nature of theory reduction, which only represents a consequences. small space of the philosophical possibilities for reduction. One interpretation of some alternatives to reduction is that they are responding A shared feature of many alternatives to reductionism is an emphasis on to the complexity of reduction that has become more apparent over the pluralist dimensions of epistemology in biology that situate past two decades (e.g., seeing explanations as inherently interlevel), and methodological or explanatory reduction as one among many necessary the fact that biologists' use of the term “reductionism” refers to different components (Dupré 1993, Kellert et al. 2006, Longino 2000, 2002, specific commitments in different cases and research contexts. Thus, for Mitchell 2003). In different ways, these positions stress how the scientific example, mechanisms approaches are another way to treat the investigation of biological phenomena demands diverse epistemic tools heterogeneity of explanation (including reductive and non-reductive without a requirement to tie it all together into fundamental physics, aspects), which was largely ignored in the literature on theory reduction macromolecular chemistry, or even molecular biology. Thus, ontological that assumed a few select examples from biological research were reduction becomes more or less unhinged from epistemological reduction representative. This heterogeneity is a pervasive feature of the history of because there is no need to demonstrate how each and every domain of biology, so that philosophical alternatives to reduction are responding in scientific inquiry is anchored in physical stuff. Scientists are part to long-standing controversies among life science investigators about epistemologically profligate, even if they are largely metaphysically the legitimacy of reductionist research strategies and modes of frugal (see Dupré 1993 and van Fraassen 2002 for differing perspectives explanation (see Section 2). The compatibility or conflict among these on science and metaphysics). The plurality of biological research various alternatives and different accounts of explanation in biology is not motivates a philosophical pluralism about biology, both in terms of the yet known (but see Bechtel 2006, 40–44), but the traditional philosophical many meanings available for different methodological and project of articulating a single notion of reduction to capture most epistemological types of reduction, and the need to have multiple essential aspects of theory structure and explanation across biology is dimensions of reductionism in order to secure empirical adequacy with unlikely to succeed. respect to biological phenomena (Grantham 1999, Kellert et al. 2006, Looren de Jong 2006, Morange 2006, Sullivan 2009, van der Steen 1999, 6. Future Prospects Wylie 1999). Arguably, the discussion of reductionism in biology is becoming more It is clear that these different kinds of “alternatives” to reductionism rather than less philosophically interesting. This is a consequence of successfully capture some features left untreated or ignored by theory recognizing the diverse conceptual landscape carved out over the past two
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decades, one that is much larger than that conceived of when only and Craver 2007). For example, an interest in the context sensitivity of Nagelian theory reduction was in view. Biological science is now more realization in philosophy of mind (Wilson 2004, ch. 6) invokes issues specialized than ever but disciplinary proliferation brings with it issues pertaining to the context objection, individuation, temporality (especially relevant to any analysis of reduction: using the same terms differently, causation versus constitution), and intrinsicality. These analyses can then disparate methodologies, distinct explanatory norms, and divergent be imported into biological contexts to argue for or against particular interests in “levels” of biological organization. It also includes an aspects of reductionism (see, e.g., Wilson 2005). acknowledgment that certain enduring biological topics like development still engender difficult questions about reductionism and new fields of One area where more work needs to be done is relating discussions of inquiry reinvigorate these discussions (e.g., synthetic biology's appeal to different kinds of hierarchies to the questions of reductionism. Biological molecular components as Lego-like building blocks in the Registry of hierarchies are diverse (Grene 1987, Korn 2002, 2005), and some areas of Standard Biological Parts). Philosophers need to recognize that a criterion biological research, such as paleontology and systematics (Valentine and of adequacy on accounts of reductionism in biology involves interpreting May 1996, see also Grantham 1999, 2004a, 2004b, 2007), have been why scientists make pronouncements about the failure of reductionism in ignored when reductionism comes into view. Paying attention to different areas of life science (see, e.g., De Backer et al. 2010).[16] temporality encourages the exploration of functional or control hierarchies in more detail (Salthe 1985, 1993, Wimsatt 2002). The There is also increasing contact between neuroscience and limitations of representing biological systems in terms of hierarchies psychologically oriented investigations (Bechtel 2008, Boogerd et al. should be explored in more depth as well (Potochnik and McGill 2012). 2002, Craver 2007). A potential prospect related to the contact between molecular neurobiology and psychology is the injection of epistemic All of these possibilities suggest more scrutiny of disciplinary considerations into philosophy of mind discussions (Godfrey-Smith heterogeneity in biological investigation relevant to reductionism. 2008). More attention to issues of representation, decomposition, and Although ecology has received some treatment (Dupré 1993, ch. 5; temporality could alter the nature of these debates. At the same time, a Mikkelson 2004), issues of decomposition and representation have not yet more explicit evaluation of metaphysical components imported from received wide attention (Lafrançois 2006). Another area related to philosophy of mind into philosophy of biology is warranted. Mediated by explanatory reduction and mechanisms in experimental research is cancer the work of Jaegwon Kim, Rosenberg incorporated the concept of biology (Bizarri et al. 2008, Moss 2002, Soto and Sonnenschein 2005, supervenience from Davidson three decades ago (Rosenberg 1978).[17] 2006). Because of the diversity of explanations found in these different Rosenberg has recently redeployed Kim's (1998) causal exclusion disciplines, the nature of scientific explanation returns with a vengeance argument in support of reductionism in biology (Rosenberg 2006; cf. (Schaffner 2006). Although only a few reductionists demand explanation Sachse 2007). Discussions of the status of downward causation and to be strictly nomological (Rosenberg 2006, Weber 2005), the subtle realization in biological systems are relevant for a better understanding of interplay between explanation and reduction will have to be treated when the intersection between epistemological and metaphysical components of ranging over diverse biological subdisciplines. Additionally, as more reduction (Craver and Bechtel 2007, Love 2012, Robinson 2005, Wilson attention is given to the diversity of investigative reasoning (or “scientific
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practice”) in and among these disciplinary contexts, the interplay between enrich science?” American Biology Teacher 70:303–305. different aspects of methodological and epistemic reduction will become Balzer, W., and C.M. Dawe (1986a), “Structure and comparison of more salient. genetic theories: (1) classical genetics”, British Journal for the Philosophy of Science 37:55–69. A final prospect concerns whether discussions of reduction in different ––– (1986b), “Structure and comparison of genetic theories: (2) the sciences will interact fruitfully. Although questions of reduction in reduction of character-factor genetics to molecular genetics”, British philosophy of physics have largely diverged from those in philosophy of Journal for the Philosophy of Science 37:177–191. biology, some connections have been drawn. For example, Sarkar has Beatty, J. (1990), “Evolutionary anti-reductionism: historical reflections”, approached quantum mechanics using his account of reductionism that Biology and Philosophy 5:197–210. was forged in a biological context (Jaeger and Sarkar 2003). A potential Bechtel, W. (1986), “The nature of scientific integration”, in W. Bechtel intersection between these discussions arises around the relations between (ed.), Integrating scientific disciplines, Dordrecht: M. Nijhoff, 3–52. parts and wholes or temporality, which have come under scrutiny from ––– (1993), “Integrating sciences by creating new disciplines: the case of philosophers focused on the physical sciences (Hüttemann 2004, Love cell biology”, Biology and Philosophy 8:277–299. and Hüttemann 2011, Rueger 2000, Rueger and McGivern 2010). Another ––– (2006), Discovering cell mechanisms: the creation of modern cell area worthy of more attention is reductive explanation in chemistry, biology. Cambridge: Cambridge University Press. which has been ignored in large part by philosophers of biology (see, e.g., ––– (2008), Mental mechanisms: philosophical perspectives on cognitive Bishop 2010, LePoidevin 2005, Ramsey 1997, Scerri 1994, 2000). neuroscience. London: Routledge. ––– (2010), “The downs and ups of mechanistic research: circadian In all these cases it seems clear that debates about reductionism in biology rhythm research as an exemplar”, Erkenntnis 73:313–328. have not reached a denouement but rather portend vigorous philosophical Bechtel, W., and A. Abrahamsen (2005), “Explanation: a mechanist discussion as the heterogeneity of issues related to its ontological, alternative”, Studies in History and Philosophy of Biological and epistemological, and methodological types are brought to bear on Biomedical Sciences 36:412–441. perennial biological topics. The task of philosophers focused on ––– (2010), “Dynamic mechanistic explanation: computational modeling reductionism in biology will be to analyze these promiscuities of of circadian rhythms as an exemplar for cognitive science”, Studies reasoning and seek to develop accounts of reduction that offer a more in History and Philosophy of Biological and Biomedical Sciences general perspective on biological knowledge and scientific inquiry. 41:321–333. Bibliography ––– (2011), “Complex biological mechanisms: cyclic, oscillatory, and autonomous”, in C.A. Hooker (ed.), Philosophy of complex systems Allen, G.E. (1975), Life science in the twentieth century. New York: (Handbook of the philosophy of science, Vol. 12), Amsterdam: Wiley. Elsevier / North Holland, 257–285. Allchin, D. (2008), “Marxism and cell biology: can political perspective Bechtel, W., and A. Hamilton (2007), “Reduction, integration, and the unity of science: natural, behavioral, and social sciences and the
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scientific progress | supervenience | teleology: teleological notions in accounts that concentrate on ontological reduction and mereological biology constitution (e.g., supervenience; see Kim 1998, 2005). In philosophy of social science, key questions include whether social phenomena can be Acknowledgments explained solely in terms of the interactions of individuals, whether different fields of social science can be reduced to economics, and Tom Doyle, Andreas Hüttemann, Ken Waters, Rob Wilson, and two whether social science as a whole can be reduced to one or more of the anonymous referees provided useful suggestions on earlier versions of natural sciences (Kincaid 1997). Regardless of whether reduction is this entry. Thanks to Naomi Scheman for the suggestion to look at considered within philosophy of biology, mind, or social science, similar Margaret Drabble's The Sea Lady. We appreciate the many colleagues ideas and arguments have been used in these different fields (e.g., who gave us valuable feedback on the earlier version of this entry. Ingo multiple realization; see Section 4.2). Brigandt's work on this essay was funded with an Izaak Walton Killam Memorial Postdoctoral Fellowship by the Killam Trusts of Canada and 3. “Let us now, if you please, imagine that a small worm lives in the with Standard Research Grant 410-2008-0400 by the Social Sciences and blood, whose sight is keen enough to distinguish the particles of blood, Humanities Research Council of Canada. Alan Love's work on the lymph, etc., and his reason to observe how each part on collision with revision of this essay was supported in part by a grant from the John another either rebounds, or communicates a part of its own motion, etc. Templeton Foundation (“Complexity, emergence and reductionism: That worm would live in this blood as we live in this part of the universe, toward a multilevel integrative analysis of the brain and cognition”; ID and he would consider each particle of blood to be a whole, and not a part. 24426). And he could not know how all the parts are controlled by the universal nature of blood, and are forced, as the universal nature of blood demands, Notes to Reductionism in Biology to adapt themselves to one another, so as to harmonize with one another in a certain way. For if we imagine that there are no causes outside the 1. James Griesemer (2000, 2002, 2011) argues for a heuristic use of blood to communicate new motions to the blood, and that outside the reduction in the attempt by scientists to relate different theories and blood there is no space, and no other bodies, to which the particles of models to one another. Although this account is clearly methodological, it blood could transfer their motion, it is certain that the blood would remain does not focus on how scientists discover molecular mechanisms or always in its state, and its particles would suffer no changes other than develop reductive explanations of wholes in terms of parts. Thus, it is those which can be conceived from the given relation of the motion of the distinct from the sense of methodological reductionism used here. blood to the lymph and chyle, etc., and so blood would have to considered always to be a whole and not a part. But, since there are very many other 2. The issue of reduction has played a substantial role in both philosophy causes which in a certain way control the laws of the nature of blood, and of mind and philosophy of social science. In the former, a central question are in turn controlled by the blood, hence it comes about that other is whether and in what sense mental phenomena can be reduced to motions and other changes take place in the blood, which result not only physical phenomena. Philosophers of mind have developed sophisticated from the mere relation of the motion of its parts to one another, but from
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the relation of the motion of the blood and also of the external causes to 7. E.g., “cellular context is important when deciphering how EGF one another: in this way the blood has the character of a part and not of a [epidermal growth factor] interacts with EGFR [epidermal growth factor whole. … all the bodies of nature can and should be conceived in the receptor]. From a general perspective, care is advisable when generalizing same way as we have here conceived the blood” (Spinoza to Oldenburg, ligand-receptor interaction results across multiple cell-lines” (Björkelund Letter 32; Wolf 1966, 210-211). et al. 2011, 1). Also, “Agents binding to the enzyme catalysing the reaction may influence this Michaelis constant [describing the enzyme's 4. “Now it is true that the ultimate elements of organized matter are reaction kinetics] … All components of the same living cell may precisely those which enter into the composition of Unorganized therewith affect the role the enzyme plays in the cell's behaviour, substances: But by the operation of a power, distinct from Gravitation, including the components that are not yet known” (Westerhoff and Kell molecular attraction, or any of the known imponderable agents which 2007, 37–38). operate on unorganized substances, these elements assume combinations of a character essentially different from those which are the result of 8. In the debate about the relations between classical and molecular ordinary chemical affinities” (Owen, Hunterian Lectures [1837] in Sloan genetics, Philip Gasper (1992) dubs this “multiple supervenience” in 1992, 209). order to contrast it with multiple realization. A different way to make a similar point is that biological entities and processes (including molecular 5. The mid-twentieth century separation of discussions about relations ones) often possess their causal properties extrinsically (i.e., due to between domains of science (Nagelian theory reduction) and relations features external to the bearer of the property). For example, a particular between parts and wholes in biology (explanatory reduction) is concretely segment of DNA is a gene as a consequence of its ability to code for a visible in David Hull's Philosophy of Biological Science (1974). Chapter functional product, which depends on both DNA elements external to this 1 is a justly famous discussion regarding the difficulties of effecting gene and non-genetic factors. Therefore, being a gene is a property of a theory reduction between classical and molecular genetics, but chapter 5, DNA segment, but an extrinsic one. “Organicism and Reductionism”, has been relatively neglected. It includes a very different set of themes, including vitalism, biological organization 9. The derivation demanded by theory reduction for molecular biology and complexity, and the relations between parts and wholes in living requires that the premises contain a purely molecular specification of the systems. total context. Although Nagel and Schaffner have explicated the notion of theory reduction, they have not shown how to effect the molecular 6. Rosenberg's argument contains several controversial premises, such as deduction. Even Schaffner's most detailed defense of reduction (Schaffner the need for strict laws in biological explanation and the distinction 1993) focuses on the condition of connectability, giving a partial account between molecular and functional biology (for criticisms, see Love 2007, of how to relate the predicate “dominance” used in classical genetics to Love et al. 2008). The intersection of natural selection and molecular expressions from biochemistry. But he does not give a single example of a biology for explanatory reductionism has been explored by Sarkar (2005 higher level statement being deducible from some lower level theory, and [1991]) with much less optimism. theory reduction requires that the condition of derivability be met. Debate
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over Schaffner's model has focused primarily on the condition of situations. connectability, especially whether a molecular characterization of the notion of a classical gene is possible. Yet as Hull (1974) makes plain, a 12. The notions of multiple realization and supervenience were originally critic of theory reduction needs no more than an argument against developed in philosophy of mind as part of a non-reductive physicalism connectability as a necessary condition on reduction, while a reductionist about mental phenomena. Whether these concepts offer an adequate has to defend derivability over and above connectability. account of the relation between mental and physical phenomena has been questioned (Kim 1992, 1998). The status of multiple realization in 10. One of Schaffner's replies to Hull regarding the one-many objection is philosophy is currently a subject of debate and may hinge on certain that the molecular context of a mechanism can be included in the metaphysical commitments about the concept of realization (Gillett 2002, premises to the extent that it matters. Wimsatt (1976a) rightly points out 2003, 2010). “Realization” takes on different roles in scientific and that stressing the inclusion of context will always rely on how the philosophical discussions (Wilson and Craver 2007) and the significance mechanisms are individuated (Hüttemann and Love 2011; see Section of these differences has not yet been analyzed for the situations of 4.3). Schaffner's move to include the total context implies that any two multiple realization frequently discussed in philosophy of biology. possible situations will have distinct overall molecular configurations, but Biological examples used in these philosophical discussions, such as eyes, others view this as the same mechanism in different contexts. Generality have often not been treated with adequate care and precision (Couch requires treating parts of different particular molecular configurations as 2005, 2009). instantiating the same type of mechanism. A flip-side of this need for generality is that the same type of mechanism can occur in different 13. “Out of over 1 million animal species, modern developmental biology contexts, possibly with a different effect. This sense of one–many has focused on a very small number which are often described as ‘model relations between molecular and higher level kinds does not necessarily organisms.’ This is because the motivation for their study is not simply to preclude some types of reduction, but explanations in molecular biology understand how that particular animal develops, but to use it as an must to be sensitive to the associated epistemic issues. example of how all animals develop” (Slack 2006, 61).
14. A less common objection concerns whether the domains being 11. Higher level laws can have exceptions: e.g., if Md, one of the reductively related are actually distinct. For example, Russell Vance molecular kinds realizing S, does not cause any of the realizers N1, …, Nj of T. Waters (1990) has argued that explaining such an exception requires (1996) has argued against the premise that classical genetics and appeal to the molecular level and therefore is a form of reductionism. This molecular genetics are separate fields or theories (e.g., “genetics is the contrasts with Fodor (1974) who argued that a reductionistic approach area of biological science that seems most immediately amenable to the encourages eliminating the higher level generality in favor of philosopher's conception of scientific reduction. The main reason for this exceptionless lower level laws. But scientists often accept higher level is that in genetics there are two clearly identifiable theories, bodies of laws despite exceptions that require appeal to the molecular level law, expressions of regularity – one molecular and one nonmolecular” precisely because they aim to address both the higher and lower level [Rosenberg 1985, 90]). While this undermines global attempts at
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reductively relating classical genetics and molecular genetics, and a holistic approach, yet today's models largely ignore how epidemics modulates how to understand local explanatory reductions, its more change individual behaviour” (Ferguson 2007, 733); “The collective general impact can be understood as a caution against presuming that two behaviour of matter can give rise to startling emergent properties that hint areas of biology are distinct in practice or distinguishable in principle (as at the nexus between biology and physics” (Coleman 2007, 379); “After is often done in theory reduction). One cannot simply assume an several decades dominated by reductionist approaches in biology, individuation of the epistemic units being related reductively. researchers are returning to the study of complex biology with a litany of new and old techniques” (Hogenesch and Ueda 2011, 407). Noble (2006) 15. For example, some explanations in developmental biology appear to represents a book-length treatment in this vein. rely on temporal representations that are not keyed to the temporal organization of mechanisms (e.g., normal stages). If so, the issue of 17. “The formalization of supervenience employed here is the application temporality in explanations cannot be reduced to the issue of temporality of one due to Jaegwon Kim” (Rosenberg 1978, 373). Referring to Kim's in a mechanism. Additionally, qualitative change in ontogeny, where paper “Nomological incommensurables” (read at Oberlin Colloquium in novel structures emerge out of distinct developmental precursors, does not 1977), Rosenberg continues in a footnote: “My debts to this paper are by appear straightforwardly amenable to a mechanisms approach. no means limited to its account of supervenience. In fact, the whole “Mechanism” also has been advocated by those discussing reductionism perspective adopted here with respect to the relation between theories in the context of evolutionary biology (Brandon 1996). involved in reduction, and the bearing of causal and mereological determinism on this relation are inspired by this paper. … The reader is 16. E.g.: “The heart provides an excellent example both of the huge referred to Kim's paper for a fuller account of supervenience and its role advances that have been made using the reductive approach and of the in ethics, aesthetics, and the philosophy of mind in general.” severe limits of this approach” (Noble 1998, 56); “Our results suggest that the cellular responses induced by multiplex protein kinase inhibitors may Copyright © 2012 by the authors be an emergent property that cannot be understood fully considering only Ingo Brigandt and Alan Love the sum of individual inhibitor-kinase interactions” (Kung et al. 2005, 3587); “Our results therefore point to the need to consider each complex biological network as a whole, instead of focusing on local properties” (Guimerà and Nunes Amaral 2005, 899); “Robustness … is one of the fundamental and ubiquitously observed systems-level phenomena that cannot be understood by looking at individual components” (Kitano 2004, 826); “The molecular reductionism that dominated twentieth-century biology will be superseded by an interdisciplinary approach that embraces collective phenomena” (Goldenfeld and Woese 2007, 369); “Understanding the dynamics of infectious-disease transmission demands
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