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Home , Catastrophism, Principles of Geology, Theory of the Earth, Uniformitarianism

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Catastrophism and " logical roots and current relevance in

VICTOR R. BAKER Department of Hydrology and Water Resources, The University of Arizona, Tucson, AZ 85721-0011, USA

Abstract, in the sciences is rooted in the view that Earth signifies its causative processes via landforms, structures and rock. Processes of types, rates and magnitudes not presently in evidence may well be signified this way. Uniformitarianism, in contrast, is a regulative stipulation motivated by the presumed necessity that science achieves logical validity in what can be said (hypothesized) about the Earth. Regulative principles, including , actualism and , are imposed a priori to insure valid . This distinction lies at the heart of the catastrophist versus uniformitarian debates in the early nine- teenth century and it continues to influence portions of the current scientific program. Uniform- itarianism, as introduced by in 1830, is specifically tied to an early nineteenth century view of inductive inference. Catastrophism involves a completely different form of inference in which hypotheses are generated retroductively. This latter form of logical inference remains relevant to modern science, while the outmoded notions of induction that warranted the doctrine of uniformitarianism were long ago shown to be overly restrictive in scientific practice. The latter should be relegated solely to historical interest in the progress of ideas.

On 4 July 1997, the Mars Pathfinder spacecraft Antarctic ice, was interpreted as showing various made a highly successful landing in the Ares Vallis indicators of possible relic biogenic activity region of Mars. The spectacular images transmitted (McKay et al. 1996). That this meteorite could be back to eager scientists at the Jet Propulsion from Mars is itself a profound legacy of catas- Laboratory, California, were immediately subjected trophic processes at human-centred scales of time to scrutiny. Within days, rather firm genetic hypo- and space, but a completely consistent with the theses were presented to the crowds of news of impact mechanics (Melosh 1984, 1985) reporters eagerly waiting to share the excitement of and confirmed by geochemical measurement science-in-the-making with millions of non- (McSween 1994). Indeed, the various organic scientists worldwide. geochemical and petrographic interpretations of The interpretation of the Pathfinder landing biogenesis, processes for which we can observe scene (Fig. 1) was completely geological. Large ample extant modern operations, are far more boulders, both angular and subrounded, were seen controversial in interpretation (McSween 1997) to be organized into distinct sedimentary patterns. than the immense meteor impact catastrophe that The smooth slopes of distant hills on the horizon launched pieces of Mars to Earth. were also interpreted. In neither case was the The ease with which these invocations of causative process inferred to be one presently catastrophism flowed for explaining Martian operative on the surface of that planet. Indeed, the features stands in sharp contrast to debates over the processes now acting on the extremely cold, dry origins of Earth's valleys, the genesis of clastic and nearly airless planet had done little to erase the sediments and the of fluid-shaped landforms bold imprint of processes last active hundreds of that contributed to the intellectual origins of million years ago. The shaped hills and boulder geology in the eighteenth and nineteenth centuries trains were clearly analogous to similar features in (Davies 1969). Some of the rhetoric in these the Channelled Scabland region of Earth. The debates led, in the earliest nineteenth century, to the origin of landforms in that region (Baker 1981) is mistaken conceptual association of cataclysmic the same origin proposed for the Martian landscape flooding hypotheses with religious dogma, when seen on television by more than a hundred million the real dogma lay in the arbitrary stipulation of people: catastrophic flooding. attributes for laws, processes and rates actually Only a few months before the Pathfinder operative in nature (Gould 1987). By substituting landing, a meteorite from Mars, collected from theoretical standards of nature for religious ones,

BAKER, V. R. 1998. Catastrophism and uniformitarianism: logical roots and current relevance in geology. 171 In: BLUNDELL,D. J. & ScoTt, A. C. (eds) Lvell: the Past is the Key to the Present. Geological Society, London, Special Publications, 143, 171-182. Downloaded from http://sp.lyellcollection.org/ by guest on September 29, 2021

172 V.R. BAKER

Fig. 1. Mars Pathfinder landing site imaged in July 1997 from the lander spacecraft. This mosaic of images shows boulders in trains and quasi-imbricate arrangement. The hills on the horizon have rounded slopes and scarps that were shaped by large-scale fluid flow. Ancient catastrophic flooding produced both the landforms and the sedimentary patterns.

well-meaning geological reformers blinded subse- and immense bars of -transported bouldery quent workers with the importance of rare, great gravel (Baker 1981). in Earth history. It was not until the Nearly coincident with the attainment of geo- Channelled Scabland debates of the 1920s that logical respectability by Bretz's hypothesis, the cataclysmic flooding re-emerged for consideration Mariner 9 spacecraft produced images of Mars as an important geomorphological process. In those displaying ancient channelways of immense size, debates , the flood advocate, insisted containing nearly the same landform assemblage as upon drawing attention to the flood evidence at the Channelled Scabland (Baker 1982). It was the field sites in eastern Washington State, regardless geological understanding of the ancient Martian of the numerous theoretical arguments to the floods (Baker & Milton 1974; Baker 1982) that led contrary (Baker 1978). The controversy was such to such ease of interpretation for the Pathfinder that Bretz's outrageous hypothesis of cataclysmic landing site. flood origins for scabland terrains of eastern Giant glacial outburst floods are now recognized Washington did not achieve general acceptance as characteristic of the terminal phases for the until the 1960s and 1970s. By then it was realized immense ice sheets that covered much of North that a whole suite of landscape features was present America and Eurasia in the last ice age. Late-glacial that could only be explained by the high-energy age flooding in the Altay Mountains of central Asia physics of immense flood flow (Baker 1973). The has recently been documented to rival or exceed diagnostic landforms included great streamlined that of the Channelled Scabland (Baker et al. 1993). hills, multiple channelways deeply scoured into Landforms formerly attributed to glacial action rock, inner channels headed by great rock cataracts alone are now recognized as the products of close Downloaded from http://sp.lyellcollection.org/ by guest on September 29, 2021

CATASTROPHISM AND UNIFORMITARIANISM 173 association between flooding and glacial ice (Shaw espoused by (1726-1797), a finan- 1994). cially successful medical doctor and chemical It is well to remember that all these revelations industrialist. Hutton devoted much of his later were achieved not by theoretical elegance in to managing his farms and to various writings, explaining the Earth, but by overcoming restrict- including his . The latter denied ions posed by existing theories. In their attempts to a role of catastrophic forces by instead invoking the enshrine fundamental principles for their science, action of existing processes as sufficient, acting nineteenth century advocates of a 'more scientific' over long time scales, to shape the surface of the geology confused simplicity of logical expression planet. with intrinsic qualities of nature. The resulting The second of the great theories prevailing in the doctrine, named 'uniformitarianism', asserted that early nineteenth century was that of the German the relatively low-intensity, frequently occurring mineralogist, Abraham Gottlob Werner (1749- processes in evidence today must be the class of 1817). Werner believed that rocks were laid down processes generally operating in the past. This in a primordial ocean, which convulsed and dogma sometimes proved an even greater impedi- subsided both intermittently and catastrophically. ment to understanding the past than the religious Variations in the intensity and nature of processes motivation that it purported to replace. The mis- explained the various succession of strata, precipi- taken need to stipulate attributes for laws, processes tation of crystalline rocks, and the like. The theory and rates actually operative in nature persists in was tied strictly to observed consequences of the science even to this day. Theories, which are presumed processes, which were thought merely to increasingly emphasized in proportion to compu- be much more intense variants of processes that tational power, serve not to tell geomorphologists could be observed today. about Earth. Rather, it is the signs of Earth itself, The Hutton and Werner controversy centred on the dirt, land and rocks, that are interpreted by substantive issues of alternative 'systems' for the , employing, of course, all manner of operations of our planet through geological time. theoretical and mechanical devices to aid in that These were both theoretical constructs, so it was interpretation. natural that concern would turn towards issues of once observed that the book of methodology in how to scientific the universe is written in the symbolic language of theories. The issue of methodology may have been mathematics. To read the book of the universe one particularly attractive to Lyell, who went on from must learn the language. However, Earth and Mars his Oxford BA in Classics to the practice of Law. are not the entire universe, nor is symbolic the He was particularly active as an advocate before the only language worthy of scientific . The bar during 1825-1827, precisely during the period language of indices, which are signs directly when he was also writing the methodological representing causative processes, comprises the polemic that comprises volume I of his Principles critical text for geological reading. The indices for of Geology. In 1827 Lyell abandoned his law career cataclysmic flooding processes are the character- to devote himself full time to his geological istic landforms and deposits emplaced by that interests. flooding (Fig. 1). This language must be learned The lawyer in Lyell must have been particularly from nature herself. Unlike the symbolic language attracted to James Hutton's advocacy of order in the of mathematics, it is not found in textbooks. It is the system espoused in his opus Theoo' of the Earth role of the to understand nature's text, not with Proofs and Illustrations (Hutton 1795): to impose upon the original document a theoretical Chaos and confusion are not to be introduced 'overstanding,' no matter how elegant or logical. into the order of Nature, because certain things appear to our partial views as being in some Lyeli's logic disorder. Nor are we to proceed in feigning causes when those seem insufficient which occur The doctrine of uniformitarianism in geology was in our experience. persuasively advocated by Charles Lyell (1797- 1875) in his influential book : It is clear, even from his somewhat tortured Being an Attempt to Explain the Former Changes writing style, that Hutton greatly admired the work of the Earth's Surface by Reference to Causes Now of Sir (Fig. 2). Newton devised an in Operation (Lyell 1830-1833). Lyell had entered ideal mechanical theory for the solar system in Oxford University in 1816 and there received his which the planets eternally cycled the Sun in first exposure to geology. He became very inter- timeless perfection. Hutton (1788, p.304) envi- ested in a debate then raging between adherents of sioned a revolutionary and cyclic system of an two alternative theories for the geological operation Earth history, 'without vestige of a beginning or of the Earth. The first of these theories had been prospect of an end'. Hutton's theory became widely Downloaded from http://sp.lyellcollection.org/ by guest on September 29, 2021

174 V.R. BAKER

in which an attempt was made to dispense entirely with all hypothetical causes, and to explain the former changes of the Earth's crust by reference exclusively to natural agents.' While he shared with Hutton, via Playfair, the goal of establishing a system for the Earth, Charles Lyell had the additional vision of a specific method whereby this would be achieved. On the eve of publication of volume I of his Principles, Lyell wrote in his letter of 15 January 1829 to Roderick Murchison (K. Lyell 1881, vol. 2, p. 234): My work .., will endeavour to establish the principle of reasoning in the science; and all my geology will come in as illustration of my views on those principles, and as evidence strength- ening the system necessarily arising out of the admission of such principles ... (the principles being) that no causes whatever have ... ever acted, but those now acting; and that they never acted with different degrees of energy from that which they now exert ... In establishing a system one must always be concerned with one's theoretical bias. How one controls this bias is essential to the quality of the theorizing. Lyell expressed his theoretical bias in a letter of 7 March 1837 to (K. Lyell 1881, vol. 2, p. 6-7): ... I was taught by Buckland the catastrophic or Fig. 2. Sir Isaac Newton statue in the chapel of Trinity paroxysmal theory, but before I wrote my first College, Cambridge University, where he was a fellow volume, I had come round, after considerable and professor. and reading, to the that a bias towards the opposite system was more philosophical ... known to Charles Lyell and many others, not in its Lyell firmly believed that the hypothesizing of original form, but in a more physical version paroxysms or catastrophes involved a presumption described by John Playfair ( 1748-1819). Trained in that 'ordinary forces and time could never explain both mathematics and physics, Playfair treated geological phenomena' (K. Lyell 1881, vol. 2, p. 3). Hutton's theory as Newtonian science, not as the To avoid this purported bias it is necessary to philosophy and theology implied by Hutton's stipulate the true nature of those forces. Lyell also original (Dean 1992). This led to several very set forth this principle in his letter of 7 March 1837 significant deviations. Whereas Hutton (1795) to Whewell (K. Lyell 1881, vol. 2, p. 3): considered his Theor 3' to be a discovered working The reiteration of minor convulsions and of nature, Playfair (1802) cast it as a human changes is, I contend, a vera causa, a force and construct of , describing physical mode of operation which we know to be true. processes, and capable of improvement. Playfair The former intensity of the same or other further presumed scientific principles in the theory terrestrial forces may be true; I never denied its a priori, in the manner of geometric (Dean possibility: but it is conjectural. I complained 1992). that in attempting to explain geological pheno- Lyell (1830), almost certainly following the mena ... there had always been a disposition to interpretation of Playfair (1802), ascribed to Hutton reason a priori on the extraordinary violence and the goal of according fixed principles to geology in suddenness of changes ... instead of attempting the manner that Newton did for astronomy (Dean strenuously to frame theories in accordance with 1992). Lyell (1830, p. 61) writes that Hutton's the ordinary operations of nature ... Theory of the Earth, '... was the first in which geology was declared to be in no way concerned The notion of vera causae, or 'true causes,' is about questions as to the origin of things; the first highly appropriate to a science (Newtonian Downloaded from http://sp.lyellcollection.org/ by guest on September 29, 2021

CATASTROPHISM AND UNIFORMITARIANISM 175 physics) that eschews the Aristotelian search for Table 1. The methods of geology, c. 1830 (Laudan 1987) knowledge of causes in a Platonic quest for essential principles. Newton himself established the Method Characteristics principle as one of the 'Rules of Reasoning' in his highly acclaimed Principia: 'We are to admit no Hypothesis Presumption of a causative state of affairs from observation of its consequent more causes of natural things than such as are both phenomena true and sufficient to explain their appearances'. For geology in the early nineteenth century this Eliminative Observational data are used to refute all principle assumed a slightly modified form induction conceivable rival explanations save one (Laudan 1987): 'No causes should be invoked in Enumerative Simple generalizations are derived from our geological reasoning unless they have real induction the data () existence (i.e. we have directly observed them) and Analogy Combining hypothesis and induction that they be adequate to produce the purported effect'. Vera causa Causes existing and sufficient to produce Clearly Lyell viewed the task of the geologist 'to the effect explain geological phenomena'. This is accomplished via principles or logical foremost of which is the following vera causa (K. Lyell 1881, vol. 2, p. 5): '... the adequacy of known considerable degree of precision, can we be causes as parts of one continuous progression to surprised that they who reason on the more produce mechanical effects resembling in kind and obscure phenomena of remote ages, should magnitude those which we have to account for ...'. wander in a maze of error and inconsistency. The way to avoid 'error and inconsistency' in Uniformity and induction geology was through strict adherence to logic. In science, according to Herschel among others of The American geologist Joseph LeConte (1877, Lyell's contemporaries, this was possible only via 1895) recognized that the source of Lyell's method- Newton's vera causa (Laudan 1987) combined ology was physics, not geology. LeConte (1895, p. with enumerative induction, perhaps allowing for 315) wrote: some analogical reasoning. Lyell (1830, p. 165) The basis of modern geology ... was undoubtedly explicitly states this position: laid down by Lyell in the idea that the study of ... the value of all geological evidence, and the 'causes now in operation' producing structure interest derived from the investigation of the under our eyes is the only sound basis of Earth's history, must depend entirely on the reasoning ... According to this view, things have degree of confidence which we feel in regard to gone on from the beginning at a uniform rate, the permanency of the laws of nature. Their much as they are going on now ... (this) view was immutable constancy alone can enable us to conceived in the spirit of the physicist.., and may reason from analogy, by the strict rules of be called physical rather than geological. induction, respecting the events of former ages ... Rachel Laudan (1987) argues persuasively that to arrive at the knowledge of general principles Lyell composed his Principles at a time when five in the economy of our terrestrial system. methodologies were competing in the science of In embracing induction, and particularly its geology. These methods, characterized in Table 1, enumerative variant, as the method of geology include hypothesis, eliminative induction, enumer- Lyell was also embracing an empiricist ative induction, analogy, and vera causa. In philosophical tradition, beginning with common with his friend, physicist and philosopher and Bishop Berkeley, extending to Hutton's of science (1792-1871), Lyell Edinburgh contemporary , and Lyell's viewed the method of hypothesis with particular own contemporary . These scorn. Of the advocates of the Wernerian 'system' philosophers held, in contrast to continental of Earth history and the catastrophist hypotheses idealists like Descartes and Kant, that all inquiry attendant thereto, Lyell (1830, p. 224) writes: starts with experience, which is then treated The popular reception of these ... sophisms ... has axiomatically. One must have a logical basis to hither to thrown stumbling-blocks in the way of reason from what is observed (sense or those geologists who desire to pursue the science 'facts') to what is unobserved. But this reasoning, according to the rules of inductive philosophy ... loosely termed 'induction', has a fundamental if authors may thus dogmatize, with impunity, on difficulty that was made explicit by David Hume. subjects capable of being determined with Hume reasoned that it was impossible ever to Downloaded from http://sp.lyellcollection.org/ by guest on September 29, 2021

176 v.R. BAKER justify a theory or law in science by experiment or positive in his invocation of uniformity as a observation. Just because one sees the sun rise each necessity for geological reasoning. The argument day does not, by itself, require that it will rise the had all the force of the following implied next day. This is the famous logical problem of syllogism: induction, which Sir (1959, p. 54) Major premise: Enumerative induction is the only summarized in terms of three seemingly valid reasoning process in incompatible principles: geology (a) Hume's discovery ... that it is impossible to Minor premise: Uniformity (vera causa) provides justify a law by observation or experiment, since the only basis for valid it 'transcends experience'; (b) the fact that enumerative induction science proposes and uses laws 'everywhere and Conclusion: An a priori doctrine of uniformity all the time' ... To this we add (c) the principle of (uniformitarianism) is necessary which asserts that in science, only for geology to be a valid science observation and experiment may decide upon the acceptance or rejection of scientific statements, including laws and theories ... Do geologists reason inductively? Popper (1959, 1969) claimed to solve the In embracing the empiricist philosophies and through his famous principle inductive methodologies of Herschel, Mill, and of falsification (Lindh 1993). In the early nine- others, Lyell rejected methodologies advocated by teenth century a common resolution was achieved other contemporary scholars. Historical accounts through the invoking of a 'uniformity'. Explanation have sometimes ignored these methodological of why this was necessary now requires some issues, since many of the alternative methodologies logical discourse. were held by those espousing catastrophist Lyell's problem of geological induction is, in hypotheses. Ironically, it took nearly 150 years for essence, that of the ascertaining of an objective many of Lyell's critics to be recognized as probability concerning the nature of all geological 'actualistic catastrophists' (Hooykaas 1970). causes (processes), i.e. the sampling of a genus (all Sedgwick ( 1831), Conybeare (1830) and Whewell geological causes) and observing how many of that (1832) were all highly critical of Lyell's a priori genus fall in a certain species, and thence con- specification of the nature of causes and indeed of cluding the probability that, in that genus, any his whole view of the nature of geological given individual will belong to that species. Note reasoning. that an objective probability is simply a ratio, Of Lyell's critics William Whewell (1794-1866) within a certain course of experience, between (a) was the most important (Fig. 3). Whewell believed the number of individuals in a species and (b) the that one discovered the logic of science through number of individuals in a genus over that species. study of its actual practice, and he devoted This is what is meant by induction. (The foregoing extensive historical research to this end (Whewell wording derives from unpublished writings by the 1837, 1840). His research led him to the partly great logician Charles S. Peirce in 1900.) idealist position that the intuition of '' in A uniformity may be most succinctly defined as science is progressive and evolving. However, a high objective probability of an objective unlike other idealists like Descartes, Whewell held probability (Peirce 1902, p. 727). Here an objective that any axioms or principles were products of probability is defined as a ratio, with a certain scientific inquiry, not starting points for such course of experience, between (a) the number of inquiry. These ideas were vehemently criticized by individuals in a species and (b) the number of John Stuart Mill (1843), who argued on a detached individuals in a genus over that species. In Lyell's logical basis that the real work of science lay in the geological problem the genus is all geological establishment of knowledge by inductive proof. causes (or processes), and the species of his interest This position was subsequently embraced by is the observed set of attributes characteristic of and other founders of logical those causes (or processes), observed generally empiricism and related strands of modern analytical because those causes are presently in operation. philosophy. Whewell's ideas were declared Lyell's goal was to achieve the most valid possible defeatist because he made science dependent upon induction, which is simply the ascertaining of the and luck. As Wettersten and Agassi highest possible probability concerning the nature (1991, p. 345) observe: '... because philosophers of all geological causes (the genus). ignored him and scientists did not write histories of Given that the above concept of uniformity was philosophy, he was forgotten'. prevalent in Lyell's day (e.g. Mill 1843), it is not Of course, it was Whewell (1832) who, in his difficult to see the reasoning that led Lyell to be so review of Lyell's principles, coined the terms Downloaded from http://sp.lyellcollection.org/ by guest on September 29, 2021

CATASTROPHISM AND UNIFORMITARIANISM 177

must themselves teach us the nature and intensity of the causes which have operated ...

Comparison of this statement to the logical description of induction will show that Whewell is denying that the kind of induction advocated by Lyell, and borrowed from physics, is appropriate to geology as a 'palaetiological science'. Note also that the point here concerns 'methodological uniformitarianism', a doctrine which many contem- porary scholars hold to be valid in modern geology. To understand what Whewell was aiming at we will have to return to a notion of 'hypotheses' that was summarily dismissed in the physics-based philosophy of inductions and uniformity. Following Charles Peirce, a scientific hypothesis may be considered to be the starting point of a question. A phenomenon is observed to have something peculiar about it. One then infers ifa certain state of affairs existed, then that phenomenon would in all probability occur. Hypothesis is the presumption of this state of affairs. Charles Peirce developed a logic of hypothesis and credited William Whewell for anticipating this logic (Peirce 1898). Whewell (1840) recognized that science was concerned with the forming of antithetical couplings between (1) the objective facts of nature and (2) new concepts suggested to Fig. 3. WilliamWhewell statue in the chapel of Trinity scientific minds. Whewell considered this process College, Cambridge University, where he was Master of to be a colligation ('binding together') of existing the College. facts that are unconnected in themselves but become connected through mental concepts. In his treatises on logic, Whewell (1858, 1860) referred to this process as 'induction', but Charles Peirce distinguished this form of synthetic inference from 'catastrophism' and 'uniformitarianism.' Whewell the 'induction' of which Hume (and later Popper) considered geology to be a 'palaetiological had spoken. Peirce accorded it the various names science', concerned with '... the study of a past 'hypothesis', 'abduction', 'retroduction', and condition, from which the present is derived by 'presumption'. causes acting in time'. Therefore, it was If we take Whewell's methodology to be a part of inappropriate to specify, via vera causa, the nature abductive or retroductive geology, we can now of those causes a priori. Whewell (1837, vol. 2, p. contrast it with the inductive methodology of Lyell 593) writes, in a vein similar to other catastrophists: and others (Table 2). The details of these In , we know causes only by their effects; approaches have been more fully described else- and in order to learn the nature of the causes where (Von Engelhardt & Zimmerman 1988; Baker which modify the Earth, we must study them 1996a,b), but here the distinction will be succinctly through all ages of their action, and not select drawn in terms of understanding versus 'over- arbitrarily the period in which we live as the standing' nature. The notion of 'overstanding' may standard for all other epochs ... be grasped by considering the answer of the physicist Niels Bohr to a question concerning the Whewell (1837, vol. 2, p. 592) goes much further reality of nature revealed by his theories. Bohr than any of his contemporaries, however, in a replied as follows (Petersen 1985, p. 305): 'It is complete rejection of Lyell's inductive logic: wrong to think that the task of physics is to find out (Lyell's) 'earnest and patient endeavor to how nature is. Physics concerns what we can say reconcile the former indication of change', with about nature'. This is overstanding; the explan- any restricted class of causes, -- a habit which he ations of science are judged by logical validity. enjoins, -- is not, we may suggest, the temper in Indeed verification of theories against nature is which science ought to be pursued. The effects logically precluded (Popper 1959, 1969). Downloaded from http://sp.lyellcollection.org/ by guest on September 29, 2021

178 V. R. BAKER

Table 2. Comparison of scient~)qc reasoning st3.'les for some earh" nineteenth century geologists

Uniformitarian overstanding Catastrophist understanding (Lyell, Herschel. Playfair) (Whewell, Sedgwick)

Observe Effects of geological causes Effects of geological causes Assume Axiomatic aspects of causes Axiomatic principles (laws of physics) (vera causa, uniformity) Discover Principles of geology (logically Causes actually operative in nature valid geological explanation) Goal To be logically valid (true) in To find out what nature says to us what we can say about nature

Geological understanding has to do with what of the Principles follows this task. The book begins nature says to us. This is interpreted through a with the youngest geological periods and develops process that begins with retroduction or abduction. facts further down the geological column from The distinction of abduction from induction, so Tertiary to Secondary to Primary. The progress is important in geology, has only been made clear by from the most secure facts to the least. This is the Charles Peirce, who has shared Whewell's neglect order of physics-based overstanding, rather than by most philosophers of science, despite his clear that of geology-based understanding. relevance of geology (Von Engelhardt & Zimmerman 1988; Baker 1996a,b). Consider How do geologists reason? Peirce's distinction of these two models of reasoning (in Burks 1958, pp. 136-137): What guides are required in the reasoning process of science? What determines the value of a theory Nothing has so much contributed to present or hypothesis in geology? For Charles Lyell and his chaotic or erroneous ideas of the logic of science intellectual successors this value must be estab- as failure to distinguish the essentially different lished by some principle of reasoning. Lyell sought characters of different elements of scientific to rid geology of error and inconsistency, to allow it reasoning; and one of the worst of these precision in explanation according to strict rules of confusions, as well as one of the commonest, logic, indeed to put geology on the same strong consists in regarding abduction and induction logical grounds as the sciences of controlled taken together (often mixed also with deduction) experimentation. Physics was the exemplar science as a simple argument. Abduction and induction for Lyell, and it remains so today for nearly all have, to be sure, this common feature, that both philosophers of science. Indeed the heritage of lead to the acceptance of a hypothesis because Lyell's appropriation of physics reasoning has observed facts are such as would necessarily or proven far more durable than the specifics of his probably result as consequences of that uniformitarian doctrine. The current physics-based hypothesis. But for all that, they are the opposite philosophical fashion of hypothetico-deductive poles of reason ... The method of either is the , developed by Popper (1959, very reverse of the other's. Abduction makes its 1969), is strongly advocated for geological research start from the facts, without, at the outset, having through appeals to logic and the probability of truth any particular theory in view, though it is (Cowan et al. 1997). motivated by the feeling that a theory is needed A widely-held methodological principle is that of to explain the surprising facts. Induction makes simplicity. For example, the highly respected its start from a hypothesis which seems to analytical philosopher (1967, p. recommend itself, without at the outset having 93) writes, 'The Principle of Uniformity dissolves any particular facts in view, though it feels the into a principle of simplicity that is not peculiar to need of facts to support the theory. Abduction geology but pervades all science and even daily seeks a theory. Induction seeks for facts. life'. Indeed, the mathematician John Playfair The structure of Lyell's Principles is clearly praised the geological theory of his friend James inductive. It starts with a vera causa, and it Hutton for its simplicity (Playfair 1802, p. 136), develops the facts that support this initial much as a physicist would praise a theory in that . The peculiar backwards organization science. Because simplicity is a principle held in Downloaded from http://sp.lyellcollection.org/ by guest on September 29, 2021

CATASTROPHISM AND UNIFORMITARIANISM 179 great esteem by analytical philosophers (Russell Is this order the result of the exertions of human 1929) and by physicists (Bridgman 1961), one skill and ingenuity: or is it inherent in the objects commonly encounters arguments that cite the themselves, so that the intelligent student of principle of simplicity in support of geological Natural History is led unconsciously, by the explanations (Newell 1967) or claims that simpler study of the animal kingdom itself, to these scientific explanations are somehow 'better' than conclusions ...? To me it appears indisputable, more complex ones. Such claims have received a that this order and arrangement of our studies are more skeptical reception from other geologists based upon the natural, primitive relations of (Anderson 1963). animal life ... The human mind is in tune with Uniformitarian simplicity, or scientific parsi- nature, and much that appears as a result of the mony, might be expressed as follows: no extra, working of our intelligence is only the natural fanciful or unknown causes should be invoked if expression of that preestablished harmony. known causes (those presently in operation and/or Note that Agassiz's scientific reasoning allows observed) will do the job. The substantive just as much order and precision to induction as consequences of this principle may be as innocuous does Lyell's uniformity. The difference is in from as the claim that the same laws of mechanics apply whence that order and precision will derive. Lyell, on Mars as on Earth. The successful landing of the following Newton and the various interpreters of Pathfinder spacecraft attests to the practical value his , that the warrant of this claim. However, the success of this very for induction lies in the precision of a logic that is limited view does not warrant the extension of the objectively detached from the objects represented principle to other claims, such as the following (Clifton 1988, p. 4): in its symbols. But a superprinciple is required to regulate the relationship of that logic to the natural In every case, responsible scientific procedure world mirrored in its explanations. Agassiz's dictates that we accept the most probable, 'human mind in tune with nature' needs no such generally simplest explanation for any pheno- principle. Nature is the source of any order that we menon in the geologic record ... Parsimony discover, and it is impossible to detach our logic demands that we attribute phenomena in the from the connection of its symbols to that order. sedimentary record to the most probable explan- Rather than suppressing that connection in a quest ation, and convulsive geologic events are, by for 'knowledge of general principles', Agassiz nature, improbable. would have the scientist learn the lesson that nature has to teach. Note how the above quote conflates notions of The American polymath Charles S. Peirce induction (probable inference), simplicity, uni- probably devoted the most intense philosophical formity and factual observation (the improbability effort to understanding Agassiz's approach to of catastrophic processes) into a proscriptive induction. Peirce actually studied classification methodological statement. Is this really how geo- with Agassiz and may have influenced some logists wish to interpret the Earth? The catastro- important writings on philosophy of geology phist philosophers cited above would hold that in a (Baker 1996a). In his 1898 lectures on Reasoning natural science, in tune with nature, the only valid and the Logic of Things Peirce describes the issue demands on our explanations are those made by as follows (Peirce 1898, pp. 176-177): nature. If nature contradicts our philosophy, parsi- mony included, it is nature that our explanations The only end of science, as such, is to learn the should follow, no matter how elegant and simple lesson that the universe has to teach it. In the philosophy. Induction it simply surrenders itself to the force (1859) recognized a principle of of facts. But it finds, at once, -- I am partly 'naturalness' in geological reasoning and applied it inverting the historical order in order to state the to the problem of classifying the divisions of process in its logical order, -- it finds I say that animals. Clearly this is a more complex problem of this is not enough. It is driven in desperation to induction (sampling genus and assigning to call upon its inward sympathy with nature, its species) than that perplexing Charles Lyell, but it is instinct for aid, just as we find Galileo at the logically equivalent. However, whereas Lyell dawn of modern science making his appeal to il appealed to a uniformity (an asserted probability to lume naturale. But insofar as it does this, the the induction), Agassiz proposes that any order in solid ground of fact fails it. It feels from that the divisions must be natural, not artificial. moment that its position is only provisional. It Although he ascribes that order to 'the Divine must then find confirmations or else shift its Intelligence', such deification is not necessary for footing. Even if it does find confirmations, they the operation of his warrant for induction. He writes are only partial. It still is not standing upon the (Agassiz 1859, p. 9): bedrock of fact. It is walking upon a bog, and can Downloaded from http://sp.lyellcollection.org/ by guest on September 29, 2021

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only say, this ground seems to hold for the contrasts only with the substantive doctrine of present. Here I will stay till it begins to give way. gradualism, it is not surprising to see modem Moreover, in all its progress science vaguely scientists embracing its position. There is nothing feels that it is only learning a lesson. The value contradictory in adhering to uniformity of law plus of Facts to it, lies only in this, that they belong to uniformity of process (actualism), while also pre- Nature; and Nature is something great, and ferring catastrophist to gradualist explanations of beautiful, and sacred, and etemal, and real,- geological phenomena. The term 'catastrophic' the object of its worship and it aspiration. only applies to the intensity and duration of a particular geological process. It does not neces- The spirit of hypothesizing in geology, captured sarily have anything to do with whether or not such so well by Peirce, is far more relevant to the a process is manifest today (actualism) or even with practice of the discipline (Baker 1996b) than is the well-known methodological claim that simpler Charles Lyell's induction and uniformity. This explanations are to be preferred to more complex spirit has been captured in the writing of Gilbert ones. This latter claim, sometimes called the (1886), Chamberlin (1890) and Davis (1926). It 'principle of scientific parsimony', is not to mean was also expressed by many of Lyell's catastrophist that some sort of high-order preference must be contemporaries. Fortunately, discoveries like those accorded simpler explanations, presumably grad- on Mars continue to reveal the inadequacies of ualistic, in contrast to more complex explanations, various uniformitarian dogmas, both substantive presumably catastrophic. Rather, it is simplicity in and methodologic, as applied to geology. terms of the more natural explanation that has proven to be the most productive methodological guide to scientific reasoning. Current trends that Conclusions invoke catastrophic hypotheses for geological It has been the thesis of this essay that the 'new phenomena are best explained as a naturalistic turn catastrophism' is rooted in a very old idea, one held to reasoning bolstered by pragmatic approaches by many of the old catastrophists: geology is about that deny the older foundational concerns (Baker what Earth has to say to us. It is tree that many of 1996b). the early nineteenth century catastrophists inter- Geology is a realistic science, not an actualistic preted their task as one of translating the thoughts one. A science that would limit itself to using the of God, but the principles of logical inference, i.e. present as the arbitrator of what counts as natural the methodological components, of their science evidence condemns itself to being actualistically are quite independent of any particular notion of unrealistic. The realism in geology derives not so God. Despite neglect by nearly all the modem much through inductive experimental contiguity as philosophers of so-called 'science', this view of through coherence and consistency of observation inference has just as much power to ensure scien- with hypothesis. The latter, which William tific progress as does the notion of methodological Whewell termed the 'colligation of facts', occurs in uniformitarianism, including doctrines of simpli- the complexity whereby nature is studied 'as is', city and actualism. rather than in the artificially defined simplified As a general observation, working scientists are 'systems' so as to be amenable to controlled prone to many misconceptions as to the relationship experimentation. To the extent that its methodology of philosophy to science. Perhaps the most perni- need not mimic that of mathematical physics, cious of these is the advocacy of foundational geology does not require notions of uniformity for principles to explain the success of science, to its successful pursuit. function as a framework for correct action, or to justify the results of science. Such presumptions of My research on catastrophic flooding has been supported foundational principles must be held on faith; they over the years by grants from the National Aeronautics always involve antithetical formulations; and they and Space Administration and the National Science Foundation. This essay is AUMIN contribution number always have substantive or 'strong' forms as well 10. as methodological or 'weak' forms. The sub- stantive forms make ontological claims about how the Earth actually behaves, while the method- References ological forms provide guidance for reasoning AGASSlZ, L. 1859. An Essay on Classification. Longman, about the Earth. The early debates on uniformi- Brown, Green, Longmans, & Roberts, and Trtibner tarianism and catastrophism by Lyell and his & Co., London. contemporaries perpetuated notions of substantive ANDERSON, C. A. 1963. Simplicity in structural geology. or ontological elements that are misplaced in In: ALBRI'I'rON,C. C. (ed.) 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