The Structure of Scientific Revolutions

Karl Popper (1902-94) set some very high standards for scientific rigor. He wanted scientists constantly to set out to disprove their work. Any scientific theory to Popper is always in the state of being not yet disproved. There is something to be said for this approach of looking for data to contradict your beliefs rather than more data that supports them. Instead Popper is using potential conflict between a theory, its predictions and actual data about the real world to drive science forward.

Popper argues that science is accountable to rigorous, objective standards, in particular falsification, which he regarded as the core of science. In the rapidly emerging field of neuro-science for instance, falsification seems rampant. However, when he looked, Kuhn couldn’t find much evidence of this falsification actually happening in practice.

Thomas Kuhn (1922-96) developed a theory of science that directly challenges that of Karl Popper. He argues that most of the time science (what he called Normal Science) operated within a set of given assumptions or “Paradigms” that were taken as given and not subject to testing. If true, this would greatly restrict the extent to which Popperian disproof could actually happen. In fact, the Paradigm as conceived by Kuhn is a sort of fundamentalist orthodoxy about “how the world is.” Normal Science is to Kuhn the process of elaboration of the Paradigm or central theory in ever more detail. A whole generation of scientists grows up with a set of common assumptions and they exhibit strong resistance to any data that might call the central Paradigm into question.

Originally printed as an article in the International Encyclopedia of Unified Science

Here Kuhn argues that science does not progress via a linear accumulation of new knowledge, but undergoes periodic revolutions, also called "paradigm shifts." Here he reviews past major scientific advances and attempts to show the “steady accretion of scientific progress via normal falsification” view of scientific progress was wrong, or, at least incomplete. Instead, he claimed that science advanced the most by occasional revolutionary explosions of new knowledge, each revolution triggered by introduction of new ways of thought so large they must be called paradigms. From Kuhn's work came the popular use of terms like "paradigm," "paradigm shift," and "paradigm change."

Paradigm:

1. a typical example or pattern of something; a model.

("there is a new paradigm for public art in this country")

2. a worldview underlying the theories and methodology of a particular scientific subject.

("the discovery of universal gravitation became the paradigm of successful science")

3. a set of linguistic items that form mutually exclusive choices in particular syntactic roles.

("English determiners form a paradigm: we can say “a book” or “his book” but not “a his book.”)

Thomas Kuhn defined paradigms as

"universally recognized scientific achievements that, for a time, provide model problems and solutions for a community of researchers,"

In short, a paradigm is a comprehensive model of understanding that provides a field's members with viewpoints and rules on how to look at the field's problems and how to solve them.

"Paradigms gain their status because they are more successful than their competitors in solving a few problems that the group of practritioners has come to recognize as acute."

Kuhn challenges the traditional understanding of how science “progresses.” He argues that the history of science is punctuated by moments of revolutionary breakthroughs ("paradigm shifts”). During these times, the entire scientific discipline is transformed.

Kuhn outlines six distinct stages with respect to scientific progress:

1. Prescience: Here there is a general lack of an unifying central paradigm.

(In a given discipline the stage only occurs once. Subsequently, there is always an existing paradigm.)

All new fields begin in Prescience, where they have begun to focus on a problem area but are not yet capable of solving it or making major advances. (Environmentalism might be seen in this light.) A field cannot make major progress on its central problems at this point because it does not know, and therefore cannot articulate what the “major problems” are. Consequently if cannot tell what an “answer” to the “problem” would look like. In this period one starts from ground zero and attempts to build a science from scratch. Because there is no paradigm to organize the data, all facts seem equally relevant. Science consists of simple data collection with no real organizing principle.

2. Normal Science: scientists operate within an overarching paradigm that guides them in their research, the formation of questions, conducting experiments. The paradigm provide them with a means ask the questions and test the answers to those questions. This is a "puzzle-solving" phase. . Guided by the paradigm, normal science is extremely productive:

"when the paradigm is successful, the profession will have solved problems that its members could scarcely have imagined and would never have undertaken without commitment to the paradigm".

In this stage, scientific progress consists in extending our knowledge of facts (as delimitated by the paradigm) working on those issues highlighted as important by the paradigm, increasing the match between the observations and the paradigm's predictions, and further development and articulation of the paradigm. Scientists doing “normal science” do not work to refute or overthrow a paradigm, or even to find out whether it is true according to Kuhn; they presuppose that it is true, and work on that assumption. Again this put Kuhn in direct opposition to Popper and the falsification vie of scientific progress.

3. Model Drift: During the period of normal science, the failure of a result to conform to the paradigm is seen not as refuting the paradigm, but as the mistake of the researcher.

A few anomalies -- cases in which the observational facts do not match up with what our paradigm has led us to expect -- can always be explained away. (The experiment was badly performed, the beakers weren't washed well enough, there must be another planet we haven't found yet, . . . )

But as they accumulate, a sense grows that something is fundamentally wrong. This, Kuhn argues, in seeming opposition to Karl Popper's notion that science “corrects” itself and progresses via the “falsifiability criterion.”

4. Model Crisis: However, Kuhn claims that, as anomalous results accumulate the paradigm comes to a “crisis stage.”

5. Model Revolution: at this point at new paradigm is formulated. The new paradigm subsumes the old set of observations, both the anomalous results and non-anomalous results into one coherent framework. However, there is resistance within the scientific community to adopt it.

6. Paradigm Shift: at this point the new paradigm is accepted and the old one discarded this is termed “revolutionary science.”

The change from one paradigm to another is not dictated by the observational data in any straightforward way. Both paradigms will have ways of accommodating the data, and proponents of the different paradigms may have different interpretations of the criteria for theory choice, so that theory A looks simpler (or more coherent with existing theory, etc.) to proponents of theory A, while theory B looks simpler to proponents of theory B.

Moreover, to some extent proponents of differing paradigms have difficulty even communicating with each other, because they will use the same terms (phonemes) to mean different things

The Kuhn Cycle

The Kuhn Cycle is preceded by the Prescience step. After that the cycle consists of the five steps:

Kuhn’s account of scientific progress has Darwinian/ evolutionary overtones.

Punctuated equilibrium: is a theory in evolutionary biology which proposes that most species will exhibit little net evolutionary change for most of their geological history, remaining in an extended state called stasis. When significant evolutionary change occurs, the theory proposes that it is generally restricted to rare and geologically rapid events of branching speciation....

Punctuated equilibrium is commonly contrasted against the theory of phyletic gradualism, which states that evolution generally occurs uniformly and by the steady and gradual transformation of whole lineages (called anagenesis). In this view, evolution is seen as generally smooth and continuous.

Kuhn also argues that rival paradigms are incommensurable. It is not possible to understand one paradigm through the conceptual framework and terminology of another rival paradigm. David Stove and other critics of Kuhn, claimed that this account of science suggests that theory choice is fundamentally irrational and relative. If rival theories cannot be directly compared in some objective way (non-paradigmatic) , then one cannot make a rational choice as to which one is better.

Kuhn stresses a notion he calls incommensurability. This gets applied, I believe, in a number of different areas but with a common pattern. Here are some of them:

A: No neutral language.

This is the most basic sense in which Kuhn uses the notion of incommensurability. The idea is that different paradigms, even if they use the same vocabulary, will use it in different ways, so that scientists committed to the differing paradigms will tend to "talk through" each other. The theoretical justification here seems to be that any aspect of a theory can affect the meanings of its terms -- there is no distinction between "analytic" and "synthetic" sentences, between sentences which merely give the meanings of terms and sentences which state facts about the world. So there is no way to give neutral definitions of words shared by different theories, definitions both theories can accept. And so it is extremely difficult (Kuhn doesn't actually say "impossible") for proponents of one paradigm to even figure out what proponents of another are really trying to say.

B: No neutral observations.

Observation is "theory-laden": what we observe depends to some extent on our theoretical commitments. Our theories provide the categories in terms of which we classify our observations, and thus to some extent affect what we see. The positivist ideal of theory choice was a situation in which two competing theories made conflicting observational predictions, a "crucial experiment" was performed, and one theory won the day while the other was refuted. On Kuhn's view, things are rarely this simple; often different theories will handle different sets of observations, and even where in some sense they overlap they may not agree in their interpretation of what is observed. (The duck-rabbit drawing is helpful in getting a feel for what Kuhn has in mind here: two people can look at exactly the same drawing and still in some sense see entirely different things.)

C: No neutral criteria for theory choice.

In The Structure of Scientific Revolutions, especially chapter IX, Kuhn appears to suggest that each "paradigm" carries with it a set of evaluative criteria on which it scores well, so that there are no neutral criteria that will decide which theory is best. "In learning a paradigm the scientist acquires theory, methods, and standards together, usually in an inextricable mixture. . . . each paradigm will be shown to satisfy more or less the criteria that it dictates for itself and to fall short of those dictated by its opponent" (pp. 109-110). In later writing, notably "Values, Objectivity, and Theory Choice," Kuhn takes what seems to be a more moderate view (though he claims that this is what he meant all along), holding that there are general criteria for theory choice on which nearly everyone can agree -- things like simplicity, scope, coherence with existing theory, etc. But he also argues that proponents of different theories may well interpret these criteria differently.

D: No neutral world.

This is the most radical of the claims Kuhn makes. He suggests that scientists committed to different paradigms in a certain sense "live in different worlds." His view here is a nuanced one; he does not deny that there is a real world which is not changed by changes in our theories or paradigms, but nevertheless insists that the world we experience and live in is changed when our theories change. (For instance, he argues that until the medieval period, there were no pendulums, but only swinging objects.)

Kuhn himself denied his view has this result. (third edition of SSR), and sought to clarify his views to avoid further misinterpretation. Freeman Dyson has quoted Kuhn as saying "I am not a Kuhnian!"

The enormous impact of Kuhn's work is evident in the changed it has effect in the vocabulary of the philosophy of science:

"paradigm shift"

"paradigm" (formerly confined to linguistics)

"normal science"

"scientific revolutions"

The frequent use of the phrase "paradigm shift" has made scientists more aware of and in many cases more receptive to paradigm changes, so that Kuhn's analysis of the evolution of scientific views has by itself influenced that evolution.

Kuhn's work has been extensively used in social sciences as well as the natural sciences. Kuhn’s analysis has been Influential in understanding the history of economic thought, for example the “Keynesian Revolution,” and in debates in political science.

Further, it suggested the fruitfulness of a social science examination of the natural sciences. Notice how much of the early philosophy of science took the form a “rational reconstruction” and was to a point, “a priori” prescription rather than close examination of what actual scientists do do. Post-Mertonian Sociology of Scientific Knowledge is once such examination.

Kuhn's work has also been used in the Arts and Humanities.

A defense Kuhn gives against the objection that his account of science from The Structure of Scientific Revolutions results in relativism can be found in an essay by Kuhn called "Objectivity, Value Judgment, and Theory Choice."[12] In this essay, he reiterates five criteria from the penultimate chapter of SSR that determine (or help determine, more properly) theory choice:

1. Accurate - empirically adequate with experimentation and observation

2. Consistent - internally consistent, but also externally consistent with other theories

3. Broad Scope - a theory's consequences should extend beyond that which it was initially designed to explain

4. Simple - the simplest explanation, principally similar to Occam's razor

5. Fruitful - a theory should disclose new phenomena or new relationships among phenomena

Nevertheless, he then goes on to show how, although these criteria admittedly determine theory choice, they are themselves imprecise. Further, in practice are used differently by individual scientists, some according more weight to one of the other.

According to Kuhn,

"When scientists must choose between competing theories, two men fully committed to the same list of criteria for choice may nevertheless reach different conclusions."

This being the case, one still cannot call these criteria "objective." If individual researchers come to different conclusions, despite the fact then none of them has done anything “epistemically improper” (ie. due to valuing one criterion over another or even adding additional criteria) then these conclusions are relative, no one of them being right or wrong.

Further still, as Kuhn note, even this picture presumes the absence of selfish or other subjective motivations, motivations of which the scientists themselves may be unaware.

Kuhn then goes on to say:

"I am suggesting, of course, that the criteria of choice with which I began function not as rules, which determine choice, but as values, which influence it."

Because Kuhn utilizes the history of science in his account of science, his criteria or values for theory choice are often understood as descriptive normative rules (or more properly, values) of theory choice for the scientific community rather than prescriptive normative rules in the usual sense of the word "criteria", although there are many varied interpretations of Kuhn's account of science.

Kuhn's metaphysical views

The fourth claim listed above, that there is no neutral world, appears to involve a commitment to some sort of metaphysical anti-realism about the empirical world, combined with an acknowledgment that there is also a real world that is not changed by our changing theories of it. Kuhn's view here is really very Kantian (except for the view that there can be different worlds for different paradigms; for Kant there is only one human "paradigm" and so only one empirical world). He shares with Kant the idea that the really real, independently existing world (for Kant, the "thing-in-itself") is completely unknowable, and that the empirical world, which is knowable, is partly constructed by our categories and concepts. (It is hard to maintain together the view that there is a thing-in-itself and the view that we cannot know anything at all about it. Just as the philosophers who followed Kant tended either to be realists who argued that we can know the real nature of things, or idealists who rejected the idea that there is a thing-in-itself, so post-Kuhnian philosophers of science tend to be either straightforward realists who think that science gives us real knowledge of the world, or anti-realists such as social constructionists who seem to reject the idea that there is a mind-independent world at all.)

Fond this on a Blog Post:

Personal Footnote: Sometime in the mid 1970s I was browsing the Philosophy of Science section of Dillon’s the London University Bookstore. I pulled out Kuhn’s book The Structure of Scientific Revolutions for a look. A professorial type appeared alongside me and glanced at what I was reading: he said: ‘Scientific revolutions, my ass’ and walked off. It was Karl Popper.