Theories as Structures:
Kuhn's Paradigms

From: What is This Thing called Science? A.F. Chalmers (1987) pp. 89 -

1. Introductory remarks

Another view that a scientific theory is a complex structure of some kind is one that has received a great deal of attention in recent years. I refer to the view developed by Thomas Kuhn, the first version of which appeared in his book The Structure of Scientific Revolutions, initially published in 1962. Kuhn started his academic career as a physicist and then turned his attention to history of science. On doing so, he found that his preconceptions about the nature of science were shattered. He came to realize that traditional accounts of science, whether inductivisit or falsificationist, do not bear comparison with historical evidence. Kuhn's theory of science was subsequently developed as an attempt to give a theory of science more in keeping with the historical situation as he saw it. A key feature of his theory is the emphasis placed on the revolutionary character of scientific progress, where a revolution involves the abandonment of one theoretical structure and its replacement by another, incompatible one. Another important feature is the important role played in Kuhn's theory by the sociological characteristics of scientific communities.

Kuhn's picture of the way a science progresses can be summarized by the following open-ended scheme:

Pre-science - normal science - crisis - revolution - new normal science - new crisis

The disorganized and diverse activity that precedes the formation of a science eventually becomes structured and directed when a single paradigm becomes adhered to by a scientific community. A paradigm is made up of the general theoretical assumptions and laws and techniques for their application that the members of a particular scientific community adopt. Workers within a paradigm, whether it be Newtonian mechanics, wave optics, analytical chemistry or whatever, practice what Kuhn calls normal science.

Normal scientists will articulate and develop the paradigm in their attempt to account for and accommodate the behaviour of some relevant aspects of the real world as revealed through the results of experimentation. In doing so, they will inevitably experience difficulties and encounter apparent falsifications. If difficulties of that kind get out of hand, a crisis state develops. A crisis is resolved when an entirely new paradigm emerges and attracts the allegiance of more and more scientists until eventually the original, problem ridden paradigm is abandoned. The discontinuous change constitutes a scientific revolution. The new paradigm, full of promise and not beset by apparently insuperable difficulties, now guides, new normal scientific activity until it too runs into serious trouble and a new crisis followed by a new revolution results.

With this resume as a foretaste, let us proceed to look at the various components of Kuhn's scheme in more detail.


2. Paradigms and normal science

A mature science is governed by a single paradigm. The paradigm sets the standards for legitimate work within the science it governs. It co-ordinates and directs the "puzzle-solving" activity of the groups of normal scientists that work within it. The existence of a paradigm capable of supporting a normal science tradition is the characteristic that distinguishes science from non-science, according to Kuhn. Newtonian mechanics, wave optics and classical electromagnetism all constituted and perhaps constitute paradigms and qualify as sciences. Much of modern sociology lacks a paradigm and consequently fails to qualify as science.
As will be explained below, it is of the nature of a paradigm to belie precise definition. Nevertheless, it is possible to describe some of the typical components that go to make up a paradigm. A further component of paradigms consists of some very general, metaphysical principles that guide work within a paradigm. Throughout the nineteenth century, the Newtonian paradigm was governed by an assumption something like, "The whole of the physical world is to be explained as a mechanical system operating under the influence of various forces according to the dictates of Newton's laws of motion", and the Cartesian programme in the seventeenth century involved the principle, "There is no void and the physical universe is a big clockwork in which all forces take the form of a push". Finally, all paradigms will contain some very general methodological prescriptions such as, "Make serious attempts to match your paradigm with nature", or "Treat failures in attempts to match a paradigm with nature as serious problems".

Normal science involves detailed attempts to articulate a paradigm with the aim of improving the match between it and nature. A paradigm will always be sufficiently imprecise and open ended to leave plenty of that kind of work to be done. Kuhn portrays normal science as a puzzle-solving activity governed by the rules of a paradigm. The puzzles will be of both a theoretical and experimental nature. Normal scientists must presuppose that a paradigm provides the means for the solution of the puzzles posed within it. A failure to solve a puzzle is seen as a failure of the scientist rather than as an inadequacy of the paradigm. Puzzles that resist solution are seen as anomalies rather than as falsifications of a paradigm. Kuhn recognizes that all paradigms will contain some anomalies (e.g. the Copernican theory and the apparent size of Venus or the Newtonian paradigm and the orbit of Mercury) and rejects all brands of falsificationism.

A normal scientist must be uncritical of the paradigm in which he works. It is only by being so that he is able to concentrate his efforts on the detailed articulation of the paradigm and to perform the esoteric work necessary to probe nature in depth. It is the lack of disagreement over fundamentals that distinguishes mature, normal science from the relatively disorganized activity of immature pre-science. According to Kuhn, the latter is characterized by total disagreement and constant debate over fundamentals, so much so that it is impossible to get down to detailed, esoteric work. There will be almost as many theories as there are workers in the field and each theoretician will be obliged to start afresh and justify his own particular approach. Kuhn offers optics before Newton as an example. There was a wide diversity of theories about the nature of light from the time of the ancients up to Newton. No general agreement was reached and no detailed, generally accepted theory emerged before Newton proposed and defended his particle theory. Not only did the rival theorists of the pre-science period disagree over fundamental theoretical assumptions but also over the kinds of observational phenomena that were relevant to their theories.

Kuhn insists that there is more to a paradigm that can be explicitly laid down in the form of explicit rules and directions. He invokes Wittgenstein's discussion of the notion "game" to illustrate some of what he means. Wittgenstein argued that it is not possible to spell out necessary and sufficient conditions for an activity to be a game When one tries, one invariably finds an activity that one's definition includes but that one would not want to count as a game, or an activity that the definition excludes but that one would want to count as a game. Kuhn claims that the same situation exists with respect to paradigms. If one tries to give a precise and explicit characterization of some paradigm in the history of science or in present-day science, it always turns out that some work within the paradigm violates the characterization. However, Kuhn insists that this state of affairs does not render the concept of paradigm untenable any more than the similar situation with respect to "game" rules out legitimate use of that concept. Even though there is no complete, explicit characterization, individual scientists acquire knowledge of a paradigm through their scientific education.

3. Crisis and revolution

The normal scientist works confidently within a well-defined area dictated by a paradigm. The paradigm presents him with a set of definite problems together with methods that he is confident will be adequate for their solution. If he blames the paradigm for any failure to solve a problem he will be open to the same charges as the carpenter who blames his tools. Nevertheless, failures will be encountered and such failures can eventually attain a degree of seriousness that constitutes a serious crisis for the paradigm and may lead to the rejection of the paradigm and its replacement by an incompatible alternative.

The mere existence of unsolved puzzles within a paradigm does not constitute a crisis. Kuhn recognizes that paradigms will always encounter difficulties. There will always be anomalies. It is only under special sets of conditions that the anomalies can develop such a way as to undermine confidence in the paradigm. An anomaly will be regarded as particularly serious if it is seen as striking at the very fundamentals of a paradigm and yet persistently resists attempts by the members of the normal scientific community to remove it. Anomalies are also regarded as serious if they are important with respect to some pressing social need. Also bearing on the seriousness of an anomaly will be the length of time that it resists attempts to remove it. The number of serious anomalies is a further factor influencing the onset of a crisis.

According to Kuhn, an analysis of the characteristics of a crisis period in science demands the competence of the psychologist much as that of an historian. When anomalies come to be seen as posing serious problems for paradigm, a penod of pronounced professional insecurity sets in. Attempys to solve the problem become more and more radical and the rules set by the paradigm for the solution of problems become progressively more loosened. Normal scientists begin to engage metaphysical and philosophical disputes and try to defend their innovations, of dubious status from the point of view of the paradigm, by philosophical arguments. Scientists even begin to express openly their discontent with and unease over the reigning paradigm. Kuhn quotes Wolfgang Pauli's response to what he saw as the growing crisis in physics around 1924. An exasperated Pauli confessed to a friend, "At the moment, physics is again terribly confused. In any case, it is too difficult for me, and I wish I had been a movie comedian or something of the sort and had never heard of physics"

Once a paradigm has been weakened and undermined to such an extent that its proponents lose their confidence in it, the time is ripe or revolution.

The seriousness of a crisis deepens when a rival paradigm makes its appearance. "The new paradigm, or a sufficient hint to permit later articulation, emerges all at once, sometimes in the middle of the night, in the mind of a man deeply immersed in crisis". (Kuhn). The new paradigm will be very different from and incompatible with the old one. The radical differences will be of a variety of kinds.

Each paradigm will regard the world as being made up of different kinds of things. Rival paradigms will regard different kinds of questions as legitimate or meaningful. As well as posing different kinds of questions, paradigms will involve different and incompatible standards. Unexplained action at a distance was permitted by Newtonians but dismissed by Cartesians as metaphysical and even occult. Uncaused motion was nonsense for Aristotle and axiomatic for Newton.

The way a scientist views a particular aspect of the world will be guided by a paradigm in which he is working. Kuhn argues that there is a sense in which proponents of rival paradigms are "living in different worlds". He cites as evidence the fact that changes in the heavens were first noted, recorded and discussed by Western astronomers after the proposal of the Copernican theory. Before that the Aristotelian paradigm had dictated that there could be no change in the super-lunar region and accordingly no change was observed. Those changes that were noticed were explained away as disturbances in the upper atmosphere.

The change of allegiance on the part of individual scientists from one paradigm to an incompatible alternative is likened by Kuhn to a "gestalt switch" or a "religious conversion". There will be no purely logical argument that demonstrates the superiority of one paradigm over another and that thereby compels a rational scientist to make the change. One reason why no such demonstration is possible is the fact that a variety of factors are involved in a scientist's judgement of the merits of a scientific theory. An individual scientist's decision will depend on the priority he gives to the various factors. The factors will include such things as simplicity the connection with some pressing social need the ability to solve some specified kind of problem and so on. Thus one scientist might be attracted to the Copernican theory because of the simplicity of certain mathematical features of it. Another might be attracted to it because he sees in it the possibility of calendar reform. A third might have been deterred from adopting the Copernican theory because of his involvement with terrestrial mechanics and his awareness of the problems that the Copernican theory posed for it. A fourth might reject Copernicus for religious reasons.

A second reason why no logically compelling demonstration of the superiority of one paradigm over another exists stems from the fact that proponents of rival paradigms will subscribe to different sets of standards metaphysical principles etc Judged by its own standards, paradigm A may be judged superior to paradigm B, while if the standards of paradigm B are used as premises the judgement may be reversed. The conclusion of an argument is compelling only if its premises are accepted. Supporters of rival paradigms will not accept each other's premises and so will not necessarily be convinced by each other's arguments. It is for this kind of reason that Kuhn compares scientific revolutions to political revolutions. This is not to say however that various arguments will not be among the important actors that influence the decisions of scientists. On Kuhn's view the kinds of factors that do prove effective in causing scientists to change paradigms is a matter to be discovered by psychological and sociological investigation.
There are a number of interrelated reasons then why, when one paradigm competes with another; there is no logically compelling argument that dictates that a rational scientist should abandon one for the other. There is no single criterion by which a scientist must judge the merit or promise of a paradigm and further proponents of competing programmes will subscribe to different sets of standards and will even view the world in different ways and describe it in a different language. The aim of arguments and discussions between supporters of rival paradigms should be persuasion rather than compulsion. I suggest that what I have summarized in this paragraph is what lies behind Kuhn's claim that rival paradigms are incommensurable".

A scientific revolution corresponds to the abandonment of one paradigm and the adoption of a new one not by an individual scientist only but by the relevant scientific community as a whole. As more and more individual scientists for a variety of reasons, are converted to the new paradigm there is an "increasing shift in the distnbution of professional allegiances. If the revolution is to be successful then this shift will spread so as to include the majority of the relevant scientific community leaving only a few dissenters These will be excluded from the new scientific community and will perhaps takes refuge in a philosophy department. In any case, they will eventually die.

Periods of normal science provide the opportunity for scientists to develop the details of a theory. However, if all scientists were and remained normal scientists, then a particular science would become trapped in a single paradigm and would never progress beyond it. This would be a serious fault, from a Kuhnian point of view. Science should contain within it a means of breaking out of one paradigm into a better one. This is a function of revolutions. Progress through revolutions is Kuhn's alternative to the cumulative progress characteristic of inductivist accounts of science.

One other function catered for in Kuhn's account is worth mentioning. Kuhn's paradigms are not so precise that they cn be replaced by an explicit set of rules, as was mentioned above. Different scientists or groups of scientists may well interpret and apply the current paradigm in a somewhat different way. This has the advantage that the number of strategies attempted will be multiplied. Risks are thus distributed through the scientific ommunity and the chances of long term success are increased. "How else," Kuhn asks, "could science hedge its bets?"

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