Part 5 (1/2)

According to Kuhn, an a.n.a.lysis of the characteristics of a crisis period in science demands the competence of the psychologist as much as that of the historian. When anomalies come to be seen as posing serious problems for a paradigm, a period of ”p.r.o.nounced professional insecurity” sets in. Attempts 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 in philosophical and metaphysical 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 (1970a, p. 84) 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 for revolution.

The seriousness of a crisis deepens when a rival paradigm makes its appearance. According to Kuhn (1970a, p. 91), ”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”. 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. The Aristotelian paradigm saw the universe as divided into two distinct realms, the incorruptible and unchanging super-lunar region and the corruptible and changing earthly region. Later paradigms saw the entire universe as being made up of the same kinds of material substances. Pre-Lavoisier chemistry involved the claim that the world contained a substance called phlogiston, which is driven from materials when they are burnt. Lavoisier's new paradigm implied that there is no such thing as phlogiston, whereas the gas, oxygen, does exist and plays a quite differen role in combustion. Maxwell's electromagnetic theory involved an ether occupying all s.p.a.ce, whereas Einstein's radical recasting of it eliminated the ether.

Rival paradigms will regard different kinds of questions as legitimate or meaningful. Questions about the weight of phlogiston were important for phlogiston theorists and vacuous for Lavoisier. Questions about the ma.s.s of planets were fundamental for Newtonians and heretical for Aristotelians. The problem of the velocity of the earth relative to the ether, which was deeply significant for pre-Einsteinian physicists, was dissolved by Einstein. 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 trans.m.u.tation of elements has an important place in modern nuclear physics (as it did in mediaeval alchemy and in seventeenth-century mechanical philosophy) but ran completely counter to the aims of Dalton's atomistic program. A number of kinds of events describable within modern microphysics involve an indeterminancy that had no place in the Newtonian program.

The way scientists view a particular aspect of the world will be guided by a paradigm in which they are 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 judgment of the merits of a scientific theory. An individual scientist's decision will depend on the priority he or she 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 in it there is the possibility of calendar reform. A third might have been deterred from adopting the Copernican theory because of an involvement with terrestrial mechanics and an awareness of the problems that the Copernican theory posed for it. A fourth might reject Copernicanism 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 and metaphysical principles. Judged by its own standards, paradigm A may be judged superior to paradigm B, whereas if the standards of paradigm B are used as premises, the judgment may be reversed. The conclusion of an argument is compelling only if its premises are accepted. Supporters of rival paradigms will not accept each others' premises and so will not necessarily be convinced by each others' arguments. It is for this kind of reason that Kuhn (1970a, pp. 93-4) compares scientific revolutions with political revolutions. Just as ”political revolutions aim to change politicial inst.i.tutions in ways that those inst.i.tutions themselves prohibit” and consequently ”political recourse fails”, so the choice ”between competing paradigms proves to be a choice between incompatible modes of community life”, and no argument can be ”logically or even probabilistically compelling”. This is not to say, however, that various arguments will not be among the important factors 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 programs will subscribe to different sets of standards and will even view the world in different ways and describe it in different languages. The aim of arguments and discussions between supporters of rival paradigms should be persuasion rather than compulsion. I suggest that what I have summarised 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 s.h.i.+ft in the distribution of professional allegiances” (Kuhn, 1970a, p. 158). If the revolution is to be successful, this s.h.i.+ft 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.

The function of normal science and revolutions.

Some aspects of Kuhn's writings might give the impression that his account of the nature of science is a purely descriptive one, that is, that he aims to do nothing more than to describe scientific theories or paradigms and the activity of scientists. Were this the case, then Kuhn's account of science would be of little value as a theory of science. Unless the descriptive account of science is shaped by some theory, no guidance is offered as to what kinds of activities and products of activities are to be described. In particular, the activities and productions of hack scientists would need to be doc.u.mented in as much detail as the achievements of an Einstein or a Galileo.

However, it is a mistake to regard Kuhn's characterisation of science as arising solely from a description of the work of scientists. Kuhn insists that his account const.i.tutes a theory of science because it includes an explanation of the function of its various components. According to Kuhn, normal science and revolutions serve necessary functions, so that science >c.u.mulative progress characteristic of inductivist accounts of science. According to the latter view, scientific knowledge grows continuously as more numerous and more various observations are made, enabling new concepts to be formed, old ones to be refined, and new lawful relations.h.i.+ps between them to be discovered. From Kuhn's particular point of view, this is mistaken, because it ignores the role played by paradigms in guiding observation and experiment. It is just because paradigms have such a pervasive influence on the science practised within them that the replacement of one by another must be a revolutionary one.

One other function catered for in Kuhn's account is worth mentioning. Kuhn's paradigms are not so precise that they can be replaced by an explicit set of rules, as was mentioned above. Different scientists or groups of scientists may well interpret and apply the paradigm in a somewhat different way. Faced with the same situation, not all scientists will reach the same decision or adopt the same strategy This has the advantage that the number of strategies attempted will be multiplied. Risks are thus distributed through the scientific community, and the chances of some long-term success are increased. ”How else”, asks Kuhn (1970c, p. 241), ”could the group as a whole hedge its bets?”

The merits of Kuhn's account of science.

There is surely something descriptively correct about Kuhn's idea that scientific work involves solving problems within a framework that is, in the main, unquestioned. A discipline in which fundamentals are constantly brought into question, as characterised in Popper's method of ”conjectures and refutations”, is unlikely to make significant progress simply because principles do not remain unchallenged long enough for esoteric work to be done. It is all very well painting a heroic picture of Einstein as making a major advance by having the originality and courage to challenge some of the fundamental principles of physics, but we should not lose sight of the fact must either involve those characteristics or some others that would serve to perform the same functions. Let us see what those functions are, according to Kuhn.

Periods of normal science provide the opportunity for scientists to develop the esoteric details of a theory Working within a paradigm, the fundamentals of which they take for granted, they are able to perform the exacting experimental and theoretical work necessary to improve the match between the paradigm and nature to an ever-greater degree. It is through their confidence in the adequacy of a paradigm that scientists are able to devote their energies to attempts to solve the detailed puzzles presented to them within the paradigm, rather than engage in disputes about the legitimacy of their fundamental a.s.sumptions and methods. It is necessary for normal science to be to a large extent uncritical. If all scientists were critical of all parts of the framework in which they worked all of the time then no detailed work would ever get done.

If all scientists were and remained normal scientists, a particular science would become trapped in a single paradigm and would never progress beyond it. This would be a serious fault, from the Kuhnian point of view. A paradigm embodies a particular conceptual framework through which the world is viewed and in which it is described, and a particular set of experimental and theoretical techniques for matching the paradigm with nature. But there is no a priori reason to expect that any one paradigm is perfect or even the best available. There are no inductive procedures for arriving at perfectly adequate paradigms. Consequently, science should contain within it a means of breaking out of one paradigm into a better one. This is the function of revolutions. All paradigms will be inadequate to some extent as far as their match with nature is concerned. When the mismatch becomes serious, that is, when a crisis develops, the revolutionary step of replacing the entire paradigm with another becomes essential for the effective progress of science.

Progress through revolutions is Kuhn's alternative to the that it took two hundred years of detailed work within the Newtonian paradigm and one hundred years of work within theories of electricity and magnetism to reveal the problems that Einstein was to recognise and solve with his theories of relativity. It is philosophy, rather than science, that comes closest to being adequately characterised in terms of constant criticism of fundamentals.

If we compare the attempts by Kuhn and by Popper to capture the sense in which astrology differs from a science, it is Kuhn's account that is the more convincing, as Deborah Mayo (1996, chapter 2) has convincingly argued. From a Popperian perspective, astrology can be diagnosed as a non-science either because it is unfalsifiable, or because it is falsifiable and shown to be false. The first will not work because, as Kuhn (1970b) points out, even in the period during the Renaissance when astrology was practised seriously, astrologers did make predictions that were falsifiable, and indeed were frequently falsified. But this latter fact cannot be taken as sufficient to rule out astrology as a science lest physics, chemistry and biology are ruled out on similar grounds, for, as we have seen, all sciences have their problems in the form of problematic observations or experimental results. Kuhn's response is to suggest that the difference between say astronomy and astrology is that astronomers are in a position to learn from predictive failures in a way that astrologers are not. Astronomers can refine their instruments, test for possible disturbances, postulate undetected planets or lack of sphericity of the moon and so on and then carry out the detailed work to see if such changes can remove the problem posed by a failed prediction. Astrologers, by contrast, do not have the resources to learn from failures in the same way. But the ”resources” that astronomers have and astrologers lack can be interpreted as a shared paradigm that can sustain a normal science tradition. Kuhn's ”normal science”, then, serves to identify a crucial element of a science.

The complementary part of Kuhn's account, ”scientific revolutions”, would seem to be of considerable merit too. Kuhn used the notion of a revolution to stress the non-c.u.mulative nature of the advance of science. The long-term progress of science does not merely involve the acc.u.mulation of confirmed facts and laws, but, on occasions also involves the overthrow of one paradigm and its replacement by an incompatible new one. Kuhn was certainly not the first to make this point. As we have seen, Popper himself stressed that scientific progress involves the critical overthrow of theories and their replacement by alternative ones. But, whereas for Popper the replacement of one theory by another is simply the replacement of one set of claims by a different set, there is much more to a scientific revolution from Kuhn's point of view. A revolution involves not merely a change in the general laws but also a change in the way the world is perceived and a change in the standards that are brought to bear in appraising a theory. As we have seen, the Aristotelian theory a.s.sumed a finite universe that was a system in which each item had a natural place and function, an important detail being the distinction between the celestial and the terrestrial. Within that scheme reference to the function of various items in the universe was a legitimate mode of explanation (for example, stones fall to the ground to reach their natural place and restore the universe to its ideal order). After the scientific revolution of the seventeenth century, the universe is an infinite one with items in it that interact by way of forces governed by laws. All explanations are by way of an appeal to those forces and laws. Insofar as empirical evidence played a role in the Aristotelian and Newtonian theories (or paradigms), in the former the evidence of the unaided senses operating under optimum conditions was regarded as fundamental, whereas in the latter, evidence acquired by way of instruments and experimentation was fundamental and often preferred over the direct deliverances of the senses.

Kuhn is undoubtedly correct, as a matter of descriptive fact, to note that there are such things as scientific revolutions that involve a change, not just in the range of claims made but also in the kind of ent.i.ties that are a.s.sumed to make up the world and the kinds of evidence and modes of explanation that are deemed appropriate. What is more, once this is acknowledged, then any adequate account of scientific progress must include an account of how the changes made in the course of a revolution can be construed as progressive. Indeed, we can draw on Kuhn's characterisation of science and pose the problem in a particularly acute way. Kuhn insisted that what counts as a problem can change from paradigm to paradigm, and also that the standards of adequacy that are brought to bear on proposed solutions to problems also vary from paradigm to paradigm. But if it is the case that standards vary from paradigm to paradigm, then what standards can be appealed to in order to judge that a paradigm in better than, and so const.i.tutes progress over, the paradigm it replaces? In precisely what sense can science be said to progress through revolutions?

Kuhn's ambivalence on progress through revolutions.

Kuhn is notoriously ambiguous on the basic question we have posed and which his own work serves to highlight. After the publication of The Structure of Scientific Revolutions Kuhn was charged with having put forward a ”relativist” view of scientific progress. I take this to mean that Kuhn proposed an account of progress according to which the question of whether a paradigm is better or not than one that it challenges does not have a definitive, neutral answer, but depends on the values of the individual, group or culture that makes the judgment. Kuhn clearly was not comfortable with that charge and, in the PostScript that he added to the second edition of his book he attempted to distance himself from relativism. He wrote (1970a, p. 206), ”later scientific theories are better than earlier ones for solving puzzles in the often quite different environments to which they are applied. That is not a relativist's position, and it displays the sense in which I am a convinced believer in scientific progress”. This criterion is problematic insofar as Kuhn himself stresses that what counts as a puzzle and a solution to it is paradigm-dependent and also insofar as Kuhn (1970a, p. 154) elsewhere offers different criteria such as 'simplicity, scope and compatibility with other specialties'. But even more problematic is the clash between the non-relativist claim about progress and the numerous pa.s.sages in Kuhn's book that read as an explicit advocacy of the relativist position, and even as a denial that there is a rational criterion of scientific progress at all.

Kuhn likens scientific revolutions to gestalt switches, to religious conversions and to political revolutions. Kuhn uses these comparisons to stress the extent to which the change of allegiance on the part of a scientist from one paradigm to another cannot be brought about by rational argument appealing to generally accepted criteria. The way in which the diagram on p. 6 changes from a staircase viewed from above to a staircase viewed from below is a modest example of a gestalt switch, but it serves to emphasise the extent to which such a switch is the very ant.i.thesis of a reasoned choice, and religious conversions are typically considered to be an a.n.a.logous kind of change. As far as the a.n.a.logy with political revolutions is concerned, Kuhn (1970a, pp. 93-4) insists that those revolutions ”aim to change political inst.i.tutions in ways that those inst.i.tutions themselves prohibit” so that ”political recourse fails”. By a.n.a.logy, the choice ”between competing paradigms proves to be a choice between incompatible modes of community life” so that no argument can be ”logically or even probabilistically compelling”. Kuhn's insistence (1970a, p. 238) that the way in which we are to discover the nature of science is ”intrinsically sociological” and is to be accomplished by ”examining the nature of the scientific group, discovering what it values, what it tolerates, and what it disdains”, also leads to relativism if it transpires that different groups value, tolerate and disdain different things. This, indeed, is how proponents of the sociology of science currently in vogue commonly interpret Kuhn, developing his views into an explicit relativism.

In my view, Kuhn's account of scientific progress as it appears in the second edition of his book, complete with PostScript, contains two incompatible strands, one relativist and one not. This opens up two possibilities. The first is to follow the path taken by the sociologists mentioned in the previous paragraph and to embrace and develop the relativist strand in Kuhn's thought, which among other things involves carrying out the sociological investigation of science the need for which Kuhn alluded but never responded to. The second alternative is to ignore the relativism and rewrite Kuhn in a way that is compatible with some overarching sense of progress in science. This alternative will require an answer to the question of the sense in which a paradigm can be said to const.i.tute progress over the one it replaces. I hope it will be clear by the end of the book which option I regard as the most fruitful.

Objective knowledge.

”The transition between competing paradigms ... must occur all at once (though not necessarily in an instant) or not at all.” I am not the only one to have found this sentence from Kuhn (1970a, p.150) puzzling. How can a paradigm change take place all at once, but not necessarily in an instant? I do not think it is difficult to find the source of the confusion embodied in the problematic sentence. On the one hand, Kuhn is aware of the fact that a scientific revolution extends over a considerable period of time involving much theoretical and experimental work. Kuhn's own cla.s.sic study of the Copernican Revolution (1959) doc.u.ments the centuries of work involved. On the other hand, Kuhn's comparisons between paradigm change and gestalt switches or religious conversions make immediate sense of the idea that the change takes place ”all at once”. I suggest that Kuhn is, in effect, confusing two kinds of knowledge here, and it is important and helpful to spell out the distinction.

If I say ”I know the date on which I wrote this particular paragraph and you do not”, I am referring to knowledge that I am aquainted with and that resides in my mind or brain, but which you are not aquainted with and is absent from your mind or brain. I know Newton's first law of motion but I do not know how to biologically cla.s.sify a crayfish. Again, this is a question about what resides in my mind or brain. The claims that Maxwell was unaware that his electromagnetic theory predicted radio waves and that Einstein was aware of the results of the Michelson-Morley experiment involve this same usage of ”know” in the sense of ”being aware of”. Knowledge is a state of mind. Closely connected with this usage, in the sense that it is also to do with the states of mind of individuals, is the issue of whether or not, and the degree to which, an individual accepts or believes a claim or set of claims. I believe that Galileo made a convinving case for the validity of the use of his telescope, but Feyerabend did not. Ludwig Boltzmann accepted the kinetic theory of gases but his compatriot Ernst Mach did not. All these ways of talking about knowledge and claims to knowledge are about the states of mind or att.i.tudes of individuals. It is a common and perfectly legitimate way of talking. For want of a better term I will call what is talked of here knowledge in the subjective sense. I will distinguish it from a different usage which I refer to as knowledge in the objective sense.

The sentence ”my cat lives in a house that no animals inhabit” has the property of being contradictory, while the sentences ”I have a cat” and ”today a guinea pig died” have the property of being consequences of the statement ”today my white cat killed someone's pet guinea pig”. In these examples, the fact that the sentences have the properties I attribute to them, in some common sense, is obvious, but this need not be so. For example, a lawyer in a murder trial may, after much painstaking a.n.a.lysis, discover the fact that one witness's report has consequences that contradict those of a second witness. If that is indeed the case, then it is the case whether the witnesses in question were aware of it or believed it or not. What is more, if the lawyer had not discovered the inconsistency, it may have remained undiscovered, so that no one ever became aware of it. Nevertheless, it would remain the case that the statements were inconsistent. Propositions can have properties that are distinct from what individuals might be aware of. They have objective properties.

We have already encountered, in chapter 1, an instance of the distinction between subjective and objective knowledge. I drew a distinction between the perceptual experiences of individuals, and what they might believe as a consequence of them, on the one hand, and the observation statements that they might be taken to support on the other. I made the point that the latter are publicly testable and debatable in a way that the former are not.

The maze of propositions involved in a body of knowledge at some stage in its development will, in a similar way, have properties that individuals working on it need not be aware of. The theoretical structure that is modern physics is so complex that it clearly cannot be identified with the beliefs of any one physicist or group of physicists. Many scientists contribute in their separate ways and with their individual skills to the growth and articulation of physics, just as many workers combine their efforts in the construction of a cathedral. And just as a happy steeplejack may be blissfully unaware of the implication of some ominous discovery made by labourers digging near the foundations, so a lofty theoretician may be unaware of the relevance of some experimental finding for the theory on which he or she works. In either case, objective relations.h.i.+ps exist between parts of the structure independently of whether individuals are aware of that relations.h.i.+p.

Historical examples from science that ill.u.s.trate this point are easy to find. It is frequently the case that unexpected consequences of a theory, such as an experimental prediction or a clash with another theory, are discovered by subsequent work. Thus Poisson was able to discover and demonstrate that Fresnel's theory of light had the consequence that a bright spot should be visible at the centre of the shadow side of a suitably illuminated opaque disc, a consequence of which Fresnel had been unaware. Various clashes between Fresnel's theory and Newton's particle theory of light, which it challenged, were also discovered. For example, the former predicted that light should travel faster in air than in water, whereas the latter predicted the reverse.

I have ill.u.s.trated a sense in which knowledge can be construed as objective by talking of the objective properties of statements, especially statements of theoretical and observational claims. But it is not only such statements that are objective. Experimental set-ups and procedures, methodological rules and mathematical systems are objective too, in the sense that they are distinct from the kinds of things that reside in individual minds. They can be confronted and can be exploited, modified and criticised by individuals. An individual scientist will be confronted by an objective situation - a set of theories, experimental results, instruments and techniques, modes of argument and the like - and it is these that the scientist must use in order to attempt to modify and improve the situation.

I do not intend my use of the term ”objective” to be evaluative. Theories that are inconsistent or which explain little will be objective according to my usage. Indeed, such theories will objectively possess the properties of being inconsistent or explaining little. Although my usage of ”objective” derives from and follows closely that of Karl Popper (see especially his 1979 text, chapters 3 and 4), I do not wish to follow him in getting involved in the tricky question of the precise sense in which these objective properties exist. Statements do not have properties in the sense that physical objects do, and spelling out the mode of existence of such linguistic objects, as well as other social constructions such as methodological rules and mathematical systems, is a tricky philosophical business. I am content to make my points at a commonsense level, using the kinds of examples I have used. This is sufficient for my purpose.