Three Types of Scientific Revolution a Kuhnian Analysis of Evolutionary Biology

Three Types of Scientific Revolution A Kuhnian Analysis of Evolutionary Biology

By Peter Block

Submitted in partial fulfillment of the Requirements for the Degree of Bachelor of Arts in Philosophy at Haverford College

Danielle Macbeth, first reader Paul Franco, second reader Peter Block Three Types of Scientific Revolution

Table of Contents

Acknowledgments

I. Introduction: ‘mixed feelings’ II. Kuhn’s disciplinary matrix III. Three criteria for scientific revolution IV. A second type of revolution: divergent revolution V. Divergent revolution in the history of developmental and evolutionary biology VI. A third type of revolution: trans‐disciplinary revolution VII. The discovery of epigenetics in developmental and evolutionary biology VIII. Support for the growth of knowledge IX. Conclusion: the work of normal science

Peter Block Three Types of Scientific Revolution

Acknowledgements

Although Kuhn spoke about scientific revolutions, his words fit quite well with how I felt about each draft of my thesis: “one must either live with incoherence or else revise a number of inter‐related generalizations.” Each draft seemed to be the result of a tumultuous revolution. Fortunately, I was surrounded with brilliant and loving friends and mentors who supported me throughout the process. Professor Danielle Macbeth, my first reader, is someone I will forever be indebted to. The wealth of time, energy and wisdom she gave me each meeting always compelled me to work harder and aim for clarity. Professor Paul Franco, my second reader, introduced me to Thomas Kuhn and the world of philosophy of science. And without him, I would still use semi‐colons; egregiously in my writing. Finally, I would like to thank my parents. Although they may never read my thesis, they have supported me wholeheartedly.

Peter Block Three Types of Scientific Revolution

Three Types of Scientific Revolution A Kuhnian Analysis of Evolutionary Biology

Kuhn’s theory of scientific revolution has received much criticism for being overly simplistic and unable to account for more subtle – and often more frequent – types of scientific change. Indeed, it is argued that modern biology has simply never experienced a ‘revolution’ in the traditional Kuhnian sense of the word. However, an overlooked aspect of Kuhn’s philosophy of science may provide the conceptual grounds to posit more nuanced types of scientific revolution that can describe more complex scientific changes. It will be argued that Kuhn’s concept of specialization provides the conceptual grounds to posit two other types of scientific revolution in his philosophy of science: divergent revolution and trans‐disciplinary revolution. The case for two new types of revolution will be situated in the field of evolutionary biology, as two events in its own historical evolution will be used to concretize divergent and trans‐disciplinary revolution.

Peter Block Three Types of Scientific Revolution

I. Introduction: ‘mixed feelings’

The publication of Structure of Scientific Revolution put forth a philosophy of science that broke with, and arguably revolutionized, the traditional conception of scientific development. Science, Kuhn asserted, does not develop towards an objective Reality through the piecemeal addition of scientific facts. Indeed, Kuhn argues, that any sort of teleological direction or monolithic accumulation of knowledge has no place in the scientific research enterprise. Rather, science oscillates between two periods of research activity: normal and revolutionary activity. Normal science constitutes periods of well‐ ordered and highly effective research. Such scientific activity is guided by ‘paradigms’, which constitute shared conceptual commitments among the scientific community and allow for research to amass a wealth of scientific facts. However, such periods of normal science are inevitably ruptured by periods of revolution in which the established scientific enterprise is overturned and replaced by a new tradition of research. Indeed, “The discovery of Newton’s second law of motion is of this sort” (Kuhn, 2000e, 15). This new scientific research enterprise possesses a set of conceptual commitments that are radically different – indeed incommensurable with – the old research enterprise’s commitments.

Thus, the revolutions that separate one scientific tradition from another precludes the possibility of a science that can accumulate knowledge of – or progress towards – a more accurate description of the world.

However, Kuhn’s model of scientific revolution has received much criticism for being overly simplistic. Philosophers, such as Bird and Toulmin, have argued that there are some changes in science that appear to fall between mere ‘theoretical articulation’, which is

Peter Block Three Types of Scientific Revolution the activity of normal science, and scientific revolution1. Moreover, philosophers of biology have argued that modern biology has simply never experienced a revolution in the traditional Kuhnian sense of the word. Ernst Mayr holds this view and states that in the biological research tradition:

The introduction of a new paradigm by no means always results in the immediate replacement of the old one. As a result, the new revolutionary theory may exist side by side with the old one. (Mayr, 2004, 165)

Mayr argues that to conceive of all science as a series of research traditions punctuated by revolutionary events of single‐paradigm replacement neglects other types, possibly other revolutionary types, of conceptual change in science.

However, Kuhn’s concept of specialization may provide an entry point into a much richer philosophy of scientific change in Kuhnian philosophy that quells concerns of an oversimplified model of science. While Kuhn’s concept of specialization only makes an appearance in his later texts and is met “with mixed feelings” (Kuhn, 2000c, 99) and “much reluctance” (Kuhn, 2000c, 98) when Kuhn begrudgingly privileges it as the indicator of the growth of scientific knowledge, his disinclination towards specialization could possibly be attributed to its seeming incongruence with his theory of scientific revolution. Kuhn’s traditional model of scientific revolution entails single paradigm replacements while specialization is precisely the proliferation of specialized disciplines.

Thus, this paper will attempt to ease Kuhn’s ‘mixed feelings’ towards specialization.

It will be argued that specialization provides the conceptual grounds to posit more nuanced types of scientific revolution to account for a larger number of conceptual changes.

Importantly, the new types of scientific revolution will still fit within Kuhn’s general

1 (Bird, 2000, 49‐63); (Mayr, 2004, 159‐169) 6

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concept of scientific revolution. Indeed, these new types of revolution will embrace

specialization in their mechanistic design and provide the means in which specialization

can account for the growth of scientific knowledge. The two types of scientific revolution that have been identified in Kuhn’s philosophy are divergent revolution and trans‐ disciplinary revolution. The former shows how scientific specialties can proliferate into more specialized and incommensurable disciplines; and the latter show how such specialized disciplines can share in anomalous phenomena, and subsequently, revolution.

Therefore, we will begin by delineating the salient conceptual commitments that not only make normal scientific research possible, but also play a pivotal role in Kuhn’s theory of scientific revolution. Theoretical models, symbolic generalizations and the lexical taxonomy of a scientific discipline will therefore be meticulously discussed. Indeed, this discussion will lay the groundwork for the rest of the paper, which will seek to show how divergent and trans‐disciplinary revolutions are possible. Thus, following the delineation of the salient conceptual commitments in a discipline, the three necessary and sufficient criteria for scientific revolution will be established. These criteria will constitute the basic mechanics of scientific revolution, for as it will be shown, all three types of revolution necessarily begin with anomalous discovery, undergo crisis, and end with radical changes in their theoretical generalizations.

With a firm understanding of the basic structure of normal science and the mechanics of scientific revolution, we will turn to Kuhn’s thoughts on specialization in science. His hypothesis that there is some second type of revolution, which accounts for the general increase in scientific specialties over time, will be expounded and confirmed through a historical analysis of the great conceptual shift in evolutionary biology in the first half of

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the 20th Century. It is here where the second type of revolution, divergent revolution, is

posited.2

Interestingly, divergent revolutions shed light on a new function of incommensurability – rather than merely barring translation between pre‐ and post‐ revolution disciplines, it serves to insulate specialties from one another. This insulation allows for each specialty to flourish in their respective normal scientific activity. This novel insight into incommensurability will show that there is a strong possibility for a third type of revolution: trans‐disciplinary revolution. It will be argued that incommensurable specialties allow for novel discoveries to be made in one specialty that are not only inconceivable in other specialties, but can also become acutely anomalous to both specialties through their shared points of commensurability. In turn, such discoveries can ultimately lead to revolution in both fields, thereby constituting a trans‐disciplinary revolution. To show this possibility, we will examine a contemporary issue in evolutionary and developmental biology to point to the possibility of trans‐disciplinary revolution. After completing our discussion on divergent and trans‐disciplinary revolution, we will be able to show how they provide the mechanistic means to show that the growth of scientific knowledge is attributable to its increasing specialization.

II. Kuhn’s Disciplinary Matrix

2Unfortunately, Kuhn’s explanations are not grounded in concrete examples, as he never provided any historical evidence for this second type of revolution: “…Kuhn does not provide examples from the history of science to support his account…” (Wray. 2005, 156.). Furthermore, I have not encountered any text in which Kuhn provides historical cases to justify his claims about specialization. However, he does claim that empirical support for the trend of increasing specialization in science “is overwhelming” and that it fits into the larger and more general trend of increasing specialization seen in all facets of society: “the development of human culture, including that of the sciences, has been characterized since the beginning of history by a vast and still accelerating proliferation of specialties.” (Kuhn, 2000d, 250.). 8

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Following much criticism for his liberal use of the concept of “paradigm” to account for the shared‐conceptual commitments that guide a scientific community’s research

activity, Kuhn adopted a more encompassing term to describe the commitments that hold a

scientific community together: a disciplinary matrix. A disciplinary matrix consists of the

different explicit and tacit commitments that are shared by a discipline’s community

members. These conceptual commitments provide the backdrop in which normal science

can carry out its function of puzzle‐solving3. While Kuhn never provides an exhaustive list

of the different types of shared commitments found within a disciplinary matrix, he does

highlight a number of commitments that a scientific community must share to maintain

normal scientific activity. I will delineate two that are most pertinent to the formation of a

scientific discipline: symbolic generalizations and theoretical models. Together, these two

commitments will be called the ‘theoretical generalizations’ of a discipline, and

importantly, they constitute the prerequisite categories for normal scientific activity. The

discussion of theoretical generalizations will lead to a discussion on the shared language of

a discipline, known as a lexicon. It will then be shown that despite the differences between

theoretical generalizations and a lexicon, they are inextricably linked in meaning and

relevance to scientific research: theoretical generalizations call forth the latter to explicate

their implied generalizations about the world.

Theoretical generalizations consist of two different subtypes of shared conceptual

commitments: symbolic generalizations and theoretical models. Such generalizations are

critical not only to normal science, but also to scientific revolution. Indeed, drastic changes

3 As Kuhn states when discussing the importance of puzzle‐solving in experimentation: “…puzzles and others like them constitute the main activity of normal science.” (Kuhn, 2000b, 140). 9

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in either subtype constitute scientific revolution. However, their importance to scientific

revolution will be the topic of conversation in the next section, and thus, we will first

explore their relevance to normal science.

Theoretical models provide the heuristic analogies or metaphysical commitments

that are shared by a discipline. Or put another way, they are the metaphors in a science, as

they juxtapose two concepts to reveal their similarities – as well as their differences –

without ever supplying an explicit list of necessary or sufficient conditions to base that

claim of similitude upon. It is for this reason that Kuhn insists that models act as more than

a pedagogical tool in science. Consider Bohr’s model of an atom, which illustrates the

relationships between the fundamental components of an atom (i.e. protons, neutrons and electrons) as different billiard balls circulating around one another. In a pedagogical light,

his model served as an effective learning device by providing a clear, yet metaphorical,

image of an atom. Yet, in light of the questions that science asks, understanding the ways in

which Bohr’s model actually corresponds to atoms in the natural world are precisely the

sorts of problems that normal science investigates. Thus, in light of how Bohr’s model prompts normal scientific activity, Kuhn states that:

…finding out which ones [laws of mechanics and electromagnetic theory] did apply and where the similarities to billiard balls lay was a central task in the development of the quantum theory. (Kuhn, 2000a, 203).

Empirically investigating the implied similarities between a model and the natural phenomena to which they refer is attempting to bring theory and fact in closer accord,

Peter Block Three Types of Scientific Revolution

which is the epitome of normal scientific research. Thus, the metaphorical parallels that

models evoke bring out the problems that scientists attempt to solve.4

This leads us to the other subtype of theoretical generalizations: symbolic

generalizations. They are the formal generalizations of a discipline, such as Newton’s

Second Law, f = ma. They are often used to demonstrate the similarity between a model

and the natural phenomena because it is through symbolic generalizations in which logic

and mathematics can be applied to empirical research. However, their use is not direct;

they must be reformulated before being applied. Thus, symbolic generalizations are not

applied to particular research questions as they generally appear. Rather, each particular

puzzle prompts a different expression of the symbolic generalization:

Though uninterpreted symbolic expressions are the common possession of the members of a scientific community, and though it is such expressions which provide the group with an entry point for logic and mathematics, it is not to the shared generalization that these tools are applied but to one or another special version of it. (Kuhn, 1977, 300).

This point can be illustrated if we consider how the symbolic generalization, f = ma takes different expressions depending on the natural phenomena it is applied to: when applied to the problem of free fall, it becomes mg = mg2s/dt2; when applied to the simple pendulum, it

2 2 2 2 2 becomes mgSinθ = mg s/dt ; or to coupled harmonic oscillators it becomes m1d s1/dt /dt

5 + k1s1 = k2(D + s2 – s1). Thus, this shows that each empirical description gained from each

different puzzle demands its own expression of the applied symbolic generalization.

Thus, taken together, it can now be seen why it is appropriate to call the theoretical

generalizations of a discipline the prerequisite categories for normal science, as they

4 For more detail on how models determine the problems that normal science concerns itself with, see: (Kuhn, 1996, 184). 5 This example is paraphrased from: (Kuhn, 1977, 300‐301). 11

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provide a discipline with starting points – in the form of puzzles – to describe the natural

world. Theoretical models juxtapose two concepts to imply that there is something similar

between them. Normal scientific research then forms empirical investigations to delineate

these implied categories of similitude and difference. Further, symbolic generalizations act

as the mediators between logic and mathematics and scientific research through their

problem‐specific expression. As such, symbolic generalizations present normal research

with puzzles in terms of their applicability to particular scientific investigations. Therefore,

theoretical generalizations present many of the problems that normal scientific research

investigates.

The scientific description that follows from theoretical generalizations is the lexicon of a scientific community. A lexicon, taken in the strictest Kuhnian sense of the word6, is the

multitude of kind terms that is created through the application of a discipline’s theoretical

generalizations to the natural world. Lexicons take on the form of a taxonomic structure, as

terms are hierarchically arranged and organized into categories that follow from the

implied generalizations of the discipline’s theoretical models and symbolic generalizations.

Thus, lexicons consist of a discipline’s explication of the similarities (and dissimilarities)

implied by its accepted theoretical generalizations. Similarly, they also consist of the

explicit expressions of a discipline’s symbolic generalizations in empirical investigations;

the different expressions of f = ma illustrated above is an example of symbolic generalizations in a lexicon. Thus, lexicons can be thought to mediate theoretical

6 When Kuhn discusses lexicons in their strictest form, he says, about their form: “…the sorts of knowledge I deal with come in explicit verbal or related symbolic forms.” (Kuhn, 2000c, 94.). It is in this sense that I employ his term lexicon – as the language of a scientific community. 12

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generalizations in their applicability to the world, and in turn, form an organized taxonomy

of interrelated7 kind terms.

It follows that lexicons and theoretical generalizations are co‐dependent on one

another to derive any meaning within a disciplinary matrix. Symbolic generalizations and

models make empirical investigation and lexical term creation possible; for it is only

against the background of such shared theoretical generalizations that scientists can base

their empirical investigations and subsequently construct a shared lexicon. Otherwise,

scientists could base their empirical investigations off of any theory of their choosing.

Indeed, as we will see, this is precisely the case in the second criterion for scientific

revolution.

Further, unlike in pure mathematical systems, symbolic generalizations cannot

stand alone in a scientific discipline (Kuhn, 1977, 299) and therefore, must be expressed

through lexical reformulations to have any relevance to the scientific community.

Furthermore, the implied similarities in a model mean nothing until they are explicated

through lexical categories, which are necessarily grounded empirical research. The billiard

balls of Bohr’s atom have no scientific import unless there are lexical terms that empirically

justify his model.

Thus, as our discussion of theoretical generalizations and lexicons comes to an end, we

will now be able to deploy these terms throughout the course of this paper. Indeed, they

are the basic elements that will be considered in each type of revolution, and as we will see,

changes in theoretical generalizations are critical to accounting for scientific revolution.

7 It should be noted that terms in a lexical taxonomy rely on other terms for meaning. This is only alluded to in pointing out the hierarchical structure of a lexical taxonomy. However, the interrelation of terms in a lexical taxonomy will be further delineated in the third criterion for scientific revolution. 13

Peter Block Three Types of Scientific Revolution

Thus, in the following section, the three necessary (and in total, sufficient) criteria for

Kuhn’s concept of scientific revolution will be delineated. These criteria will outline the

basic mechanics of scientific revolution, which will provide us with a conceptual

‘measuring stick’ to evaluate and determine the possibility of two other types of scientific

revolution: divergent and trans‐disciplinary revolution.

III. The Three Criteria for Scientific Revolution: 1. Anomalous Discovery Revolution begins with anomalous discovery. Otherwise, a discipline would find no

reason to change course, let alone be revolutionized; for disciplines never seek to improve

or amend their set of conceptual commitments unless seriously challenged. Thus,

anomalous discoveries, which are the accidental discoveries that violate a scientific

community’s shared conceptual commitments, are necessary to spark revolution. They can

arise within (almost) any of the shared conceptual commitments of a discipline, but they

typically take the form of an empirical discovery that challenges the community’s

theoretical generalization. However, anomalous discovery is not sufficient for revolution,

indeed, it is only the beginning.

2. Crisis

Crisis, which is the recognition that an anomalous discovery is in serious conflict

with some part of the disciplinary matrix, must follow from anomalous discovery in order

for revolution to be actualized. Thus, the recognition of a crisis‐provoking anomaly causes

the scientific community to refocus its attention to the assumed conceptual commitments that have been violated. Consequently, the community’s attempt to resolve a crisis‐

provoking anomaly obscures the relevance and applicability of the shared conceptual

commitments in question, as an increasing number of divergent articulations of the

Peter Block Three Types of Scientific Revolution anomaly are formed in which “no two of them [are] quite alike, each partially successful, but none sufficiently so to be accepted by the group” (Kuhn, 1996, 82‐83). Thus, crisis is the emergence of conflicting theoretical interpretations that each attempt to account for the critical anomaly that has brought its discipline’s conceptual commitments into question.

3. Incommensurability via changes in theoretical generalizations

As was briefly mentioned in our first discussion of theoretical generalizations in normal science, the formation of new theoretical generalizations is critical to scientific revolutions. Indeed, Kuhn points out that all scientific revolutions involve: “…a central change of model, metaphor, or analogy – a change in one’s sense of what is similar to what, and of what is different” (Kuhn, 2000e, 30). They establish – without explicitly delineating – the basic taxonomic order of a lexicon by juxtaposing a theoretical concept and the natural world, thereby leaving the explication of their similarities and differences for normal science. Therefore, a revolutionary alteration in a discipline’s theoretical generalizations is a change in what “is intrinsic to the language itself and that is thus prior to anything quite describable as description or generalization” (Kuhn, 2000e, 32) and results in incommensurable views of the world. Thus, scientific revolutions are constituted primarily by the creation of new theoretical generalizations because they bring about locally incommensurable lexical taxonomies.

The Copernican revolution provides a strong example of revolutionary change as change in theoretical generalizations. Furthermore, it shows how theoretical generalizations result in locally incommensurable lexical taxonomies, which is absolutely critical to Kuhn’s account of revolution. Prior to the Copernican revolution, Ptolemy’s geocentric model of the universe, which placed the earth at the center of the universe, was

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the theoretical generalizations shared by astronomers. However, Copernicus’ heliocentric

model replaced Ptolemy’s model of the universe, thereby revolutionizing the field of

astronomy. Consequently, the entire lexical categories that empirically described the

universe were changed:

Before it occurred, the sun and moon were planets, the earth was not After it, the earth was a planet, like Mars and Jupiter; the sun was a star; and the moon was a new sort of body, a satellite. (Kuhn, 2000e, 15)

By placing the sun at the center of the universe, Copernicus’ theoretical model called forth a

new lexical taxonomy to account for the physical bodies in the universe: lexical terms that

populated old categories, such as ‘planet’, were changed and new categories, such as

‘satellite’, were created. The earth was now like Mars and Jupiter, rather than being the

fixed point of the universe.

The change from one theoretical generalization to another – from the geocentric

model to the heliocentric model – made for entirely different lexical taxonomies, which

Kuhn would describe as locally incommensurable. Local incommensurability8 implies

partial untranslatability, as Kuhn states: “there is no language, neutral or otherwise, into

which both theories, conceived as sets of sentences, can be translated without residue or

loss.” (Kuhn, 1982, 670).

Translation problems arise primarily from the interrelation of terms in a lexical

taxonomy. If one attempted to translate the term ‘planet’ without ‘residue or loss’ into

Ptolemy’s lexical taxonomy, one must also translate its related terms, such as ‘earth’ and

8 Incommensurability originates in Greek geometry. It means ‘no common measure’ between magnitudes. Thus, Kuhn uses the notion of incommensurability to indicate that there is no common measure between two disciplines’ lexicons. 16

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‘Jupiter’, to preserve its meaning.9 However, attempting to translate Copernicus’ terms

‘planet’, ‘earth’ and ‘Jupiter’ into Ptolemy’s lexical taxonomy would create irreconcilable

strain in attempting to correspond analogous terms between lexicons. For example,

Ptolemy’s term ‘planet’ does not contain the term ‘earth,’ while ‘earth’ is a ‘planet’ in

Copernicus’ lexical taxonomy. Even more, to translate ‘moon’ – without reside or loss –

from Copernicus’ lexical taxonomy into Ptolemy’s would be impossible, as Copernicus’

taxonomy places the ‘moon’ in a category that is nonexistent in Ptolemy’s taxonomy. Thus,

Kuhn calls Ptolemy’s astronomy locally incommensurable with Copernicus’ astronomy

because the lexical taxonomies can neither be fully translated into one another nor into a

neutral language.

Therefore, change in theoretical generalizations constitutes a scientific revolution,

as they are the conceptual commitments that call forth a lexicon. In so doing, they bring

about a new lexical taxonomy to characterize the world, which will result in local

incommensurability with the old lexical taxonomy.

IV. A second type of revolution: divergent revolution

With the criteria for scientific revolution delineated, we can now use them to evaluate

the possibility of two other types of scientific revolution. Thus, let us turn to Kuhn’s

observations on scientific specialization, which will point us to a second type of scientific

revolution: divergent revolution. Science, Kuhn observes, exhibits a general trend of

increasing in the number of specialties over time. He goes on to hypothesize that this trend

indicates a second type of scientific revolution – one in which the old discipline is replaced

9 As we found earlier, terms do not merely gain meaning from the properties ascribed to them, but also from the other lexical terms they are related to in their taxonomy. 17

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by two new disciplines, which are both incommensurable with the old discipline as well as

with one another:

The transition to a new lexical structure…permits the resolution of problems with which the previous structure was unable to deal. But the domain of the new structure is regularly narrower than that of the old, sometimes a great deal narrower. What lies outside of it becomes the domain of another scientific specialty, a specialty in which an evolving form of the old kinds remains in use. (Kuhn, 2000d, 250)

The type of revolution Kuhn is describing provides the groundwork for the second type of

revolution we are aiming to delineate, namely divergent revolution: two new specialties emerge from an old discipline. Importantly, the traditional application of incommensurability (i.e. one that forms between pre‐ and post‐revolution disciplines) is exhibited by both newly specialized disciplines in relation to the old discipline that they birthed from: one specialty is incommensurable with the old discipline insofar as it forms theoretical generalizations around the anomalous phenomena that could not be addressed

by the old discipline; and the other specialty becomes one that addresses ‘what lies outside’

of the other specialty. Indeed, the latter specialty (i.e. the one that addresses ‘what lies

outside’) is not merely a specialized form of the old discipline. Rather, it applies an evolved

form of the old discipline’s kinds and as such, possesses a different lexicon; thus, it should

be considered incommensurable with the old discipline. Although divergent revolutions

create two specialties instead of one discipline, which is the case for the traditional type of

scientific revolution, divergent revolutions still satisfy all three criteria for scientific

revolution, and therefore prove to be a type of Kuhnian revolution: anomalous discovery is

needed to provoke a crisis in the discipline (criteria #1 and #2), which in turn, leads to the

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creation of new disciplinary matrices incommensurable with the pre‐revolution

disciplinary matrix (#3).

However, the importance of incommensurability between pre‐ and post‐ revolution

disciplines needs to be carefully examined to show that the third criterion is actually satisfied in a divergent revolution. Such incommensurability is critical to Kuhn’s account of scientific revolution, and thus, both specialties that emerge from a divergent revolution must show to be incommensurable with the old discipline. Otherwise, the increase in specialties would be nothing more than a ‘division in scientific labor’ in the established discipline. Thus, before we turn to an actual case of divergent revolution, we should first examine an apparent case of divergent revolution to highlight the importance of pre‐ and

post‐revolution incommensurability.

Up until the early 20th Century, physiology assumed that it was only through the

nervous system that the body coordinated its functions.10 However, the discovery of

‘secretin’ proved to be an anomalous discovery, as it showed that:

…the functions of the body were normally coordinated not only by the nervous system, but also by the mediation of specific chemical agents formed in, and transmitted from, one organ to others by way of circulation, conveying a message intelligible only to those cells equipped to capture the ‘chemical messenger’ and decipher the encoded instructions for modification and activity. (Gregory, 1977, 105)

The discovery of secretin demonstrated that there was an entirely distinct physiological

system from the nervous system that could coordinate bodily functions via ‘chemical

messengers’ like secretin. This system could not be assimilated into physiology’s

disciplinary matrix, as both its theoretical assumptions and lexical taxonomy centered on

10 Brad Wray points out that “…the taxonomy physiologists worked with reflected this” (Wray, 2005, 156). Thus, as their lexical taxonomy shows, physiology was conceptually committed to the notion that the nervous system was the physiological form of communication that could account for bodily function. 19

Peter Block Three Types of Scientific Revolution the nervous system. Indeed, the possibility of body coordination being controlled by something other than neural firings was inconceivable for physiology.11 A number of different theories were proposed to account for the phenomena, many of which sought to reconcile the new discovery with the nervous system (Gregory, 1977, 106). Ultimately, the specialized discipline of endocrinology was formed to precisely account for ‘secretin’ and the new system of coordination. It proposed a new theoretical model to explain how a molecule like secretin could communicate chemical messages to different organs in a body without acting through the nervous system. And thus, the endocrine system was born.

Importantly, endocrinology’s theoretical model (i.e. the endocrine system) was necessarily incommensurable with physiology’s model of the nervous system, as it called forth an entirely new lexical taxonomy. New categories (i.e. ‘hormones’ and ‘exocrine glands’) and terms (i.e. ‘secretin’) were created that had no corresponding category or term in the physiological model.

Taken together, it would appear that the divergence of endocrinology and physiology is a case of divergent revolution. Indeed, it satisfies the first two criteria for scientific revolution: the crisis‐provoking discovery of secretin violated physiology’s conceptual commitment to the nervous system (criteria #1 and #2). Furthermore, it results in the formation of incommensurable specialties, which resolve the crisis‐provoking anomaly. However, physiology itself was not made incommensurable with its old form. As

Wray points out, “…the traditional study of physiology was, to a large degree, left very much intact as it was before the discovery” (Wray, 2005, 157). Thus, it cannot be seen that

11 As Wray explains: “The existing taxonomy, built on the assumption that the functions of the body are coordinated by the nervous system, was not fit to explain the phenomena under consideration” (Wray, 2005, 157). 20

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any discipline was revolutionized in the Kuhnian sense, as there was no incommensurable

break with the old tradition of physiology. Endocrinology only truncated the number of

phenomena for which physiology could explain. Thus, the old discipline simply became more specialized. Indeed, this case of specialization is a perfect illustration of ‘nature being cut at its joints.’ Replacement of the established discipline for another incommensurable discipline is necessary for all scientific revolutions, be it in the traditional Kuhnian sense or in divergent revolution.

Thus, as we now have a sense of an apparent case of divergent revolution, let us now turn to the historical event that gave rise to the contemporary disciplines of evolutionary and developmental biology. Indeed, it will provide a concrete example of a divergent revolution because incommensurability functions not only between pre‐ and post‐

revolution disciplines, but also between the two newly formed disciplines.

V. Divergent revolution in the history of developmental and evolutionary biology

At the turn of the 20th Century, evolutionary biology was in a state of Kuhnian crisis.

Its theoretical models were provided by Darwin’s theory of evolution, which held that

descent with modification (i.e. evolution) occurs through natural selection. The mechanism

for evolutionary change (i.e. natural selection) asserted that the traits an organism

acquired could be passed on to future generations, and subsequently influence the

evolutionary outcome of its species. Thus, it found that biological developmental

adaptations were perfectly continuous with evolutionary biological changes. As such,

developmental and evolutionary biological research was contained within the same

disciplinary matrix.

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However, its theoretical assertion that adaptive developments (i.e. traits acquired in

an organism’s life) could be inherited never generated any empirical support. When

Darwin attempted to provide a more articulate theoretical model to explain how adaptive

developments occurred, experimental data demonstrated its implausibility.12 Indeed, the

persistent failure to articulate its theoretical generalizations through empirical research

became a crisis‐provoking anomaly.13

Out of evolutionary biology’s state of crisis emerged two new disciplinary matrices:

developmental and evolutionary biology. Importantly, the division between developmental

and evolutionary biology resolved the crisis‐provoking anomaly in the old discipline of

evolutionary biology by denying the possibility of inheriting adaptive developments. Thus,

evolutionary biology and developmental biology became distinct specialties, as their

respective fields of research contained almost no conceptual overlap. Furthermore, the two

specialties were both incommensurable with the old model of evolutionary biology. This is

seen in how the two new specialties adopted new theoretical generalizations.

In the new specialty of evolutionary biology, two theoretical generalizations – the

first being a theoretical model and the second being a symbolic generalization – were

adopted into its disciplinary matrix and now provide the primary points of

incommensurability with the old discipline of evolutionary biology:

1. Weismann barrier: genes in the germ‐line (i.e. genes contained in sperm and ova cells) can be inherited and genes in the somatic‐ line (i.e. genes in all other cells in

12 This theoretical model was known as Darwin’s theory of ‘pangenesis.’ See: (Jablonka and Lamb, 2005, 13‐ 16). 13 A persistent failure to articulate theory is a type of crisis‐provoking anomaly. See Alexander Bird’s delineation of the four types of anomalies that can lead to a Kuhnian revolution: Bird, 2000, 43‐44.; and for a historical account of the crisis, see: (Reid, 1985, 201– 222). 22

Peter Block Three Types of Scientific Revolution

the body) cannot be inherited. Thus, adaptive developments, which act on somatic‐ cell lines, cannot be inherited. 2. Wendy‐Steinberg principle: evolutionary changes can be quantified by tracking the fluctuation in gene frequencies within a population.14

The new disciplinary matrix therefore held that evolution can be studied by tracking the change in germ‐line gene frequencies within a population. Thus, the new disciplinary matrix’s theoretical generalizations create incommensurability with the old discipline in two ways. First, the old disciplinary matrix (of evolutionary biology) held that adaptive developments could be inherited, which is denied within the new disciplinary matrix of evolutionary biology. Only germ‐line genes are inherited and such genes are not affected by adaptive developments. Second, the new symbolic generalization provided the new discipline a powerful new methodology to study evolutionary change. Thus, the points of incommensurability in the respective disciplines’ lexical taxonomies can easily be found because – in many cases – the old discipline’s lexical taxonomy simply does not have categories or terms that can translate many terms contained in the new lexicon, such as

‘gene frequency’ or ‘somatic‐line and germ‐line gene’. Furthermore, the second newly formed specialty, developmental biology, was also incommensurable with the old discipline of evolutionary biology. It acquired new theoretical generalizations that resulted in an incommensurable lexical taxonomy with the old discipline’s lexicon. Theoretical models such as cell differentiation15, cell growth,16 and morphogenesis17 have resulted in a lexical

taxonomy that contains terms that are untranslatable – hence incommensurable – in

14 These conceptual commitments are given historical context in: (Reid, 1985, 201– 222). 15 Cell differentiation is the theoretical model that accounts the different cell types in the body such as blood cells, hepatic cells, neural cells, and so forth. 16 Cell growth is the theoretical model that explains how one cell can proliferate into many cells of the same type (i.e. how a population of cell type can form). 17 The theoretical model that explains how an organism organizes its various cell types into a structured body. 23

Peter Block Three Types of Scientific Revolution

relation to the old discipline’s lexical taxonomy. Therefore, the new theoretical

generalizations constitutive of the new disciplines of evolutionary and developmental

biology make them incommensurable with the old discipline of evolutionary biology.

Furthermore, the two specialties are also incommensurable with one another, for if

we recall the words of Kuhn, which were used earlier to describe the relationship between

new specialties: “What lies outside of it [one specialty] becomes the domain of another

scientific specialty” (Kuhn, 2000d, 250). Developmental biology investigated what was

found ‘outside of the new discipline’ of evolutionary biology. In turn, they both developed

new theoretical models to account for their different areas of study, thereby calling forth

incommensurable lexical taxonomies. Some terms in evolutionary biology’s lexical

taxonomy, such as ‘gene frequency’ and ‘genetic drift’, simply have no corresponding term

in developmental biology’s lexicon. Conversely, new terms created in developmental

biology, such as ‘epigenetic regulation’, have no place in evolutionary biology’s new lexicon.

Thus, this conceptual shift in evolutionary biology provides a concrete example of

divergent revolution because both specialties are incommensurable with the old discipline

of evolutionary biology, as well as between one another18. Importantly, Kuhn’s

hypothesized revolution that facilitates specialization has been concretely shown. As we

will find later, this model of scientific revolution provides the essential mechanism for

Kuhn’s account of the growth of scientific knowledge. However, we can now turn to

another aspect of specialization, which is highlighted by the new type of scientific

revolution: incommensurability between contemporaneous disciplines. This new function

18 Recall how the physiology and endocrinology case make for only an apparent case of divergent revolution. Although endocrinology became a new specialty that was incommensurable with physiology, physiology never evolved to become incommensurable with an old form of itself. Rather, it merely had the number of natural phenomena for which it described slightly truncated by the birth of endocrinology. 24

Peter Block Three Types of Scientific Revolution creates for the possibility of a third type of revolution – trans‐disciplinary revolution – to which we will now turn.

VI. A third type of revolution: transdisciplinary revolution

Trans‐disciplinary revolution shows that a discovery in one discipline can become a crisis‐invoking anomaly in another. Thus, what distinguishes trans‐disciplinary revolution from the first two types of scientific revolution is the location of anomalous discovery: whereas anomalous discovery and revolution occur in the same discipline for the first two types of scientific revolution, in trans‐disciplinary revolution, anomalous discovery occurs initially outside of the discipline‐to‐be‐revolutionized. Indeed, we will find that the location of anomalous discovery is not coincidental in the sense that it could have occurred in either discipline involved in a trans‐disciplinary revolution. It will be argued that the anomalous discovery could only have occurred in the discipline that initially discovers the anomaly.

This point will rely on the incommensurability that surrounds such contemporaneous disciplines. However, before getting to this point, it must first be shown how a discipline’s discovery can become another discipline’s anomaly, and this requires showing that there is some degree of commensurability between the otherwise incommensurable specialties.

Let us first recall how a discovery becomes anomalous. In order for a discovery to become anomalous, it must violate the discipline’s theoretical generalizations in some way.

Importantly, violation does not mean simply unexplainable. Discoveries that cannot be explained are discovered all the time by researchers in a discipline and are simply ignored.

Even more, discoveries are made all of the time in disciplines outside of a particular discipline that exceed its explanatory powers (and are therefore ignored). Indeed, the inability to account for discoveries outside of one’s discipline is the natural product of

Peter Block Three Types of Scientific Revolution

increased specialization: incommensurable specialties necessarily form to explain different

natural phenomena.

Thus, whether considering a discovery that affects one or two disciplines, the

discovery must have some degree of commensurability with the discipline or disciplines’

theoretical generalizations to be considered anomalous. Although the physiology case was

deemed an apparent case of divergent revolution, its anomalous discovery of secretin

demonstrates this point quite clearly. When physiologists discovered secretin, they found

that it violated their conceptual commitment to the primacy of the nervous system in

commanding bodily functions. However, to the extent that the discovery of secretin

provided an alternative mode of communication that could control body functioning, it was to this degree commensurable with the established theoretical model. This bit of commensurability made the anomaly relevant to the established theoretical model and brought to light its critical incommensurability with the established model. Therefore, in order to establish the possibility of a trans‐disciplinary revolution, there must be some points of commensurability between the two involved disciplines.

Now that we have established that trans‐disciplinary revolution requires some degree of commensurability between the two involved disciplines, we can now show that the discovery of an anomalous phenomenon, which leads to trans‐disciplinary revolution, could only have occurred within the discipline that made the discovery. We will therefore move back to the concept of incommensurability, which occurs between contemporaneous specialties. Incommensurability between contemporaneous disciplines lets disciplines flourish, as a community of scientists can focus their attention on – and only on – the accepted theoretical generalizations in their discipline. Indeed, as we have seen, theoretical

Peter Block Three Types of Scientific Revolution generalizations provide the implied similarities and differences between a theoretical model and the world, or in the case of symbolic generalizations, they provide the formal generalization that can in turn be expressed to fit with the particular puzzle. Thus, different theoretical generalizations evoke different implied similarities, which generates different scientific puzzles, different experimental techniques, and in turn, different empirical outcomes. As Kuhn explains, different ‘paradigms’ (or as we have been calling them, different theoretical models) already partially determine the direction that scientific experimentation will take, which creates for different experimentation:

Science does not deal in all possible laboratory manipulations. Instead, it selects those relevant to the juxtaposition of a paradigm with the immediate experience that that paradigm has partially determined. As a result, scientists with different paradigms engage in different concrete manipulations. (Kuhn, 1996, 126)

Different ‘paradigms’ partially predetermine different laboratory manipulations, which result in ‘different concrete manipulations,’ which in turn leads to concretely different results. Thus, incommensurability insulates a research community to the exploration of only the nuances that are called forth by their theoretical generalizations and this allows specialized disciplines to make discoveries that simply could not be discovered in other specialties.

Thus, trans‐disciplinary revolution plays off of the incommensurability and commensurability between contemporaneous disciplines. As we have shown, some degree of commensurability is needed between the otherwise incommensurable disciplines to allow for trans‐disciplinary revolution. If there is no such commensurability, the discovery of an anomaly in one discipline will not be found anomalous in another discipline, as the discovery will have no grounds to make its anomaly appear relevant to the otherwise

Peter Block Three Types of Scientific Revolution

incommensurable discipline. Furthermore, the incommensurability between the

contemporaneous disciplines makes it possible for a discipline to discover something that

simply cannot be discovered in the other discipline.

VII. The discovery of epigenetic inheritance in developmental and evolutionary biology

We can now turn to a contemporary issue in developmental and evolutionary

biology in which a discovery in the former discipline appears to be a crisis‐provoking

anomaly in both disciplines. Thus, the discovery provides strong grounds to assert the

possibility of trans‐disciplinary revolution.

New discoveries19 in developmental biology are showing that there are non‐DNA regulatory factors – known as ‘epigenetic marks’20 – that can be passed on from one

generation to the next. The new discoveries have been generally termed ‘epigenetic

inheritance.’ However, before exploring the inter‐disciplinary implications of the discovery

of epigenetic inheritance, we should first demonstrate that the discovery of epigenetic

inheritance could only have been made in developmental biology. We can prove this by

showing how such discoveries are conducive to the theoretical generalizations and lexical

taxonomy of developmental biology, and in contrast, could not even be a possible anomaly

in evolutionary biology.

19 Genetic imprinting and chromosomal methylation are two examples that show how epigenetic marks can be inherited. (Jablonka and Lamb, 2005, 137‐146). Furthermore, Importantly, some of these epigenetic marks have been found to be highly responsive to environmental stresses. In mouse models, it has been shown that altering a pregnant mouse’s diet to include more or less of a particular methyl mark (i.e. feeding the mouse with high levels of methyl‐rich food such as betaine, methionine, and folic acid) increases the proportion of newborn mice with yellow fur, which is a phenotypic trait that is directly correlated to epigenetic methylation. See: (Waterland and Jirtle, 2003, 5293–5300); (Wolff et al., 1998, 949–957). 20 The word itself – epigenetics – sheds light on its meaning: the prefix “epi‐” is Greek for above or on. Thus, epigenetics is that which acts on (or above) the genes. Thus, they are called ‘epigenetic marks’ because the molecules are ‘marking’ (i.e. binding to) DNA sequences, which then alters the expression pattern of the DNA sequence. 28

Peter Block Three Types of Scientific Revolution

Much of developmental biology concerns itself with how cells regulate their genes.

Indeed, one of its central theoretical generalizations is its theoretical model for cell differentiation, which explains how the great diversity of cell types in the human body (but also in all cellular organisms) can be attributed – almost entirely – to epigenetic forms of regulation. Thus, the new discoveries are showing that some of these ‘epigenetic marks’ can be passed on from one generation to the next would be an anomalous discovery that could conceivably emerge within developmental biology’s research activity.

In contrast, the theoretical generalizations in evolutionary biology could never make such a discovery. Evolutionary biology studies the alterations in gene frequencies at the population level to track and determine evolutionary change and have developed new theoretical models to account for this change. Such theoretical generalizations do not even include for the possibility of epigenetic forms of regulation to emerge in its scientific practices.

Nevertheless, the discovery of epigenetic inheritance has shown to be acutely anomalous not only to developmental biology, which discovered the phenomenon, but also to evolutionary biology. This trans‐disciplinary impact of the discovery of epigenetic inheritance can be explained by the shared theoretical generalization that had originally spurred their divergence: ‘only germ‐line genes can be inherited.’ Thus, the discovery that epigenetic marks could be inherited violated this shared conceptual commitment to become anomalous in both developmental and evolutionary biology. Furthermore, new

Peter Block Three Types of Scientific Revolution theoretical models are being proposed to help makes sense of this anomalous discovery.21

Thus, the first two criteria for scientific revolution have been satisfied.

However, it is not clear how this crisis‐provoking anomaly will be resolved, as the two specialties are still caught in a ‘Kuhnian crisis’. Thus, it is possible that revolution might not even occur. Nevertheless, by the very fact that a discovery in one discipline has become acutely anomalous in another, the possibility of trans‐disciplinary revolution has been affirmed. Therefore, while there are no grounds to assert that trans‐disciplinary revolution actually occurs due to a lack of historical evidence, we can still posit the conditions necessary for the possibility of trans‐disciplinary revolution, which were already touched upon in the previous section. First, some degree of commensurability is needed in order to allow for a discovery in one discipline to affect another discipline, which is otherwise incommensurable. Second, the anomalous discovery is discipline specific. This, in turn, makes it possible for a discipline to discover an anomaly that could never be discovered in another discipline, yet still become an anomaly for that discipline. Third, if either a newly formed discipline is to emerge through some sort of fusion of the two disciplines22 or if the

21 The most prominent theoretical model that is challenging the current disciplinary matrix of evolutionary biology is ‘the extended evolutionary synthesis.’ First, it has not replaced the current model of evolutionary biology. And second, it is disputed to what degree it even is challenging the current model. Massimo Pigliucci argues that the ‘extended synthesis’ is only a revision to the current theoretical model of evolutionary biology, see: (Pigliucci, 2007, 2753‐2749). However, Lindsay Craig argues that the foundation of currently established evolutionary biology is facing “significant, perhaps insurmountable challenges” (Craig, 2010, 1) from the extended evolutionary synthesis, among other challenging models. See: (Craig, 2010, 1‐ 7) 22 Kuhn offers insight into what could happen if a revolution like trans‐disciplinary revolution occurred. He discusses the possibility of a new specialty that forms from the convergence of two different specialties: “Or else a new specialty has been born at an area of apparent overlap between two preexisting specialties…At the time of its occurrence this second sort of split is often hailed as a reunification of the sciences….As time goes on, however, one notices that the new shoot seldom or never gets assimilated to either of its parents. Instead, it becomes one more separate specialty” (Kuhn, 2000c, 97) Thus, according to Kuhn’s hypothesis, trans‐ disciplinary revolution would lead to more specialties, even if it initially appears to be a ‘reunification’ of two specialties.

Peter Block Three Types of Scientific Revolution two disciplines simply undergo individual revolutions, incommensurability through the creation of new theoretical generalizations must be seen between the old and new traditions. Thus, the third condition for scientific revolution must be satisfied, regardless of the number or form that the new discipline(s) take(s). Otherwise, there will be no grounds to call it a scientific revolution. Indeed, this would be analogous to the physiology and endocrinology case in which physiology did not break from the old tradition of physiology following the outgrowth of endocrinology. As such, it was not possible to refute assertions that such a conceptual change is anything more than ‘nature being cut at its joints.’

VIII. Support for the growth of scientific knowledge

Thus far, we have shown how two new types of scientific revolution are possible: divergent and trans‐disciplinary revolution. Importantly, we can now see how these two new types of revolution provide ample support for Kuhn’s account of the growth of knowledge in science. Kuhn claims that it is precisely the pattern of increased specialization that accounts for the growth of knowledge in science. The inevitable incommensurability that arises between pre‐ and post‐revolution disciplines prevents any claims that knowledge is accumulating or corresponding to a fixed Reality, as it precludes recourse to some common measure – be it translation of two disciplines’ lexicons into one another or into a neutral language. Rather, Kuhn asserts, the problem‐solving capacity exhibited by the total number of incommensurable specialties provides the appropriate indicator for the growth of scientific knowledge (Kuhn, 2000c, 98‐99). As Kuhn says:

“Proliferation of [lexical] structures…is what preserves the breadth of scientific knowledge; intense practice at the horizons of individual worlds is what increases its depths”(Kuhn,

2000c, 250). Thus, the increasing number of scientific specialties allows science to

Peter Block Three Types of Scientific Revolution

continually expand the range of natural phenomena it explores and the

incommensurability that arises between such disciplines allows specialties to rigorously explicate their respective theoretical generalizations.

Previously, Kuhn’s traditional model for scientific revolution in which one disciplinary matrix is replaced by another incommensurable disciplinary matrix (i.e. the Copernican

Revolution), not only failed to account for, but also seemed to be at odds with, Kuhn’s claims to how scientific knowledge develops over time. How could an increase in the number of specialties account for the growth of knowledge if scientific revolution occurred via the replacement of one discipline with another? This question has now been answered by expounding Kuhn’s original intuitions and indentifying a second type of scientific

revolution: divergent revolution. It provides a new theoretical model of scientific revolution that can help account for the diversity of incommensurable specialties in science, and subsequently, how scientific knowledge can grow in both breadth and depth.

Indeed, it provides a most fitting mechanism to account for increased specialization: crisis‐ provoking anomaly gives rise to a new specialty that specializes in accounting for anomaly, old discipline evolves to account for all that falls beyond new specialty’s theoretical generalizations. Moreover, there is also no reason to imagine that divergent revolution can only be limited to the formation of two specialties, it could be quite possible that two or three or more specialties could form and ‘specialize’ according to the anomalous discovery.

Furthermore, trans‐disciplinary revolutions quite possibly provide another, albeit more nuanced, model of revolution that supports the general pattern of increased specialization in science: some discoveries can transcend the incommensurable boundaries between

Peter Block Three Types of Scientific Revolution

disciplines, induce scientific revolution, and possibly result in the formation of more

scientific specialties.

IX. Conclusion: the work of normal science

We have attempted to show that Kuhn’s philosophy of science can account for more

conceptual changes in science than is presumed in his two‐period division of normal and

paradigm‐replacement revolution. Indeed, we have identified the possibility for two novel

models for scientific revolution: divergent and trans‐disciplinary revolution. Divergent

revolution was grounded in historical evidence, as it provided a clear account of how

evolutionary biology was revolutionized into two new specialties in the first half of the 20th

Century. Furthermore, while the discovery of epigenetic inheritance in developmental biology and its subsequent impact on evolutionary biology is too ‘contemporary’ to confirm trans‐disciplinary revolution, the mere fact that one discipline’s discovery be another’s anomaly affirms trans‐disciplinary revolution’s possibility.

Importantly, neither of these types of revolutions broke from either Kuhn’s theory of scientific revolution or even his observations on specialization in science. In terms of the former, the three criteria for scientific revolution were used as a conceptual ‘measuring stick’ to make sure that the proposed models fit with Kuhn’s concept of scientific revolution. Furthermore, in terms of the latter, both types of disciplines were identified through Kuhn’s concept of specialization and have subsequently shown to affirm its importance in science. Kuhn’s intuitive insight into a second type of revolution led to the explication of divergent revolutions; and the novel function of incommensurability between contemporaneous disciplines – a function only possible if specialization is assumed – plays a critical role in facilitating trans‐disciplinary revolution.

Peter Block Three Types of Scientific Revolution

Furthermore, the two types of disciplines provide the mechanisms to account for

the growth of scientific knowledge. Divergent revolutions show how incommensurable

specialties can proliferate and trans‐disciplinary revolutions show how disciplines can

converge, and according to Kuhn, form new specialties. We have therefore shown that

Kuhn’s philosophy is much richer than his traditional notion of scientific revolution.

However, Kuhn’s insights into specialization already laid the groundwork – or one could say, provided the theoretical model – for the discovery of divergent and trans‐disciplinary revolutions. Indeed, their discovery was nothing more but the work of normal science.

Peter Block Three Types of Scientific Revolution

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