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The Philosophy of Scientific Revolutions

Anastasios Economou describes how Thomas Kuhn changed the way we think about science.

Before the publication of Thomas Kuhn’s book The Structure of Scientific Revolutions in 1962, the philosophy of science was dominated by a combination of ideas that came to be known as the received view. This was a loose, but nevertheless sophisticated, collection of theories about the methodology, aims and practice of science. The received view could be summarised in the following points:

1) Realism. (a) The ‘realist’ thinks there is an intrinsic reality in the world and even unobserved physical entities not accessible to our unassisted senses (such as electrons or magnetic fields) can, and do, have real existence. (b) A more extreme version of realism maintains that, in addition, there is a unique best description of this real world expressed in a ‘true’ theory.

2) Cumulativity. This principle asserts that there is a continuous accumulation of scientific knowledge and that science builds on what is already known. This position is connected with extreme realism (position 1b above), as it is natural to believe that as we accumulate more knowledge, the truth-content of our theories increases and an eventual, stepwise homing in to an ultimate true theory can be achieved.

3) Rationalism. According to the rationalist, there is a unique, timeless and universal criterion, called the demarcation criterion, with respect to which the relative merits of competing scientific theories can be assessed. Only those theories that satisfy the demarcation criterion belong to the domain of science. Opinions varied over what this criterion actually was. Karl Popper, for example, claimed that only theories which have the potential to be disproved by contrary observations are scientific.

4) Context of justification and context of discovery. This thesis is closely related to rationalism and goes as follows: there is a sharp distinction between the psychological and social circumstances in which a discovery is made (context of discovery or external history of science) and the logical basis for confirming belief in the actual discovery (context of justification or internal history of science). The aim of science is to test, confirm and justify theories using rational criteria while ignoring any interfering social and psychological factors; thus, only the context of justification (internal history) is of interest to scientists.

5) Observation-theory distinction. According to this doctrine, observational (or experimental) reports are objective and independent of any background theory the observers (or experimenters) might possess.

6) Foundations. Further to the previous point, observation and experiment provide the foundations for the confirmation of hypotheses and theories.

7) Precision. Scientific concepts and terms have fixed meanings in science, largely independent of the theory in which they are used.

No single philosopher or scientist held all these views simultaneously. However, all were strongly supported by one philosopher or another. For instance, the Logical Positivists emphasised points 3-7 while Karl Popper strongly maintained positions 1-4. These ideas were so influential that they formed the basis of a widespread popular conception of science.

Kuhn’s alternative view

Some of these doctrines had been challenged by various philosophers long before the publication of The Structure of Scientific Revolutions. However, only in Thomas Kuhn’s book was a coherent alternative approach proposed and developed. It was a happy accident that the book’s publication came at a time when some philosophers were beginning to realise that the received view was, in fact, in a stalemate.

The limitation of the received view was that it saw philosophy of science merely as an attempt to examine rationally how science should be done. At the same time, the descriptive side of the philosophy of science (the study of the actual historical evolution of the aims, standards and methods of scientists) was almost totally ignored. So, the main weakness of the traditional approach was its inability to provide an adequate explanation of scientific progress. Kuhn’s novel approach, despite being opposed and criticised by some leading philosophers of science, was widely regarded as providing a solution to this problem. Kuhn saw historical progress in science happening as follows.

The formation of a new science is predated by disorganised activity with different theories competing with each other (this he called the pre-science level). This stage is followed by the domination of a particular paradigm ; a paradigm is a combination of theories, assumptions, values, techniques and working practices that the scientific community finally come to adopt (normal science level). Scientists working within the adopted paradigm will try to account for new phenomena and develop novel theories to accommodate new experimental data. However, with time, anomalies will develop within the paradigm (unaccountable phenomena, theories disproved by experimental data and so on). Eventually, serious and unresolved anomalies will accumulate and, at a certain point in time, it will be realised that the paradigm is no longer viable (crisis level). The crisis will be resolved when a new paradigm emerges and is adopted by the scientific community; the sudden transition from the old problematic paradigm to the promising new one is called a scientific revolution or ‘gestalt switch ’. Normal science will prevail in the new paradigm until enough anomalies accumulate to create a crisis followed by a new revolution.

So what consequences does Kuhn’s alternative image of science have for the received view? They can be summarised as follows:

Precision, in the sense defined in position 7 above, was challenged by Kuhn; instead, he introduced the notion of incommensurability. What is meant by incommensurability is that successive and competing paradigms cannot be directly compared with each other and translated into each other. This idea is based on the point that the meaning of scientific concepts and terms will depend on their place in a particular theory (ie meaning is theory-bound ). A typical example is the notion of an electron: in the particle theory, the electron was considered as a particle, a notion apparently incompatible with the wave theory which regarded the electron as a kind of wave. In the theory accepted nowadays (wave-particle duality) the electron is seen as having both wave and particle characteristics. But obviously what you mean by ‘electron’ depends on which theory you accept. Competing theories provide completely different ‘ways of looking at the world’. The notion of incommensurability is central to the philosophy of Kuhn and has far-reaching implications regarding his challenge to the received view.

Kuhn also denied position 3 (the ahistorical, universal requirement for rationality). Although he did not deny that there are criteria for choosing a particular paradigm (such as its problem solving ability, simplicity and predictive power), he maintained that the nature of these criteria, and the relative significance assigned to each of them, will depend on the values of the scientific community that will make the decisions. The judgments of the scientific community, in turn, are influenced by the constantly changing values of society at large. The ‘gestalt switch’ will, therefore, depend on the priorities each society assigns to different aspects of competing paradigms and as such will have a historical, social and timedependent character. In the sense that the criteria for evaluating theories are relative, Kuhn is a relativist.

When gestalt switches occur, older theories are usually abandoned. This happens because the answers provided by the abandoned theories may not be important to the community any more and mainly because the old theories are incommensurable (ie in a sense incompatible) with the new paradigm. However, a paradigm is refined and developed when normal science prevails. Thus, Kuhn denied that science is cumulative, except in the periods of normal science (position 2).

The very notion of relativism implicitly suggests that the extreme realist position (ie the requirement for a unique true theory, position 1b) is undermined. For, when a revolution occurs, different competing theories exist and which one finally prevails will depend on social and historical criteria, not truthfulness. Combined with incommensurability and the rejection of cumulativity, this leads to the conclusion that the truth-content of successive paradigms does not increase so that there is no hope of reaching an ultimate ‘true’ theory. It is interesting to note that Kuhn’s approach doesn’t directly threaten the idea of a real world (thesis 1a), but it does suggest that there can’t be a unique theory to describe the reality of this external world.

Also related to the relativist position is the objection to the sharp distinction between discovery and justification (point 4). Kuhn based his objection on his thesis that justification, far from being totally dependent on timeless criteria of pure rationality, is partly determined by evolving social values. On the other hand, rational criteria, as well as psychological and social factors, may come into play in the phase of a scientific discovery.

The observation-theory distinction was rejected by Kuhn (point 5). Any observation has to be expressed in some form of language. However, to state an observation, however simple, one requires some theoretical background in order to relate the thing observed to other concepts in the chosen language. Take the observation that “The sky is blue”, for instance. In order to have a proper physical understanding of the word ‘blue’, one has to realise that it refers to a particular, narrow and sometimes arbitrary range of wavelengths in the light spectrum. This qualification is important because it removes the meaning of ‘blue’ from the realm of direct experience and connects it to a theoretical framework involving the theory of colours. In addition, to confirm the truth of the observation in an objective way, a spectrometer would have to be used, which in turn would imply an extensive background knowledge of both the phenomenon under observation and of the theory of optics. So observation presupposes theory or to put it another way, observation is theory-laden. It can therefore be maintained that observations are as fallible as the background theories they presuppose and, as such, cannot provide a secure basis for the construction of scientific theories (point 6).

It is clear that Kuhn’s initial intention was not to embark on a negative critique of the traditional philosophy of science. His aim was to provide a positive, novel, builtfrom- scratch philosophy of science based on different foundations and viewing the world from a different angle. The resulting relativism and the blurring of the theoryobservation and discovery-justification distinctions that so annoyed the supporters of the received view were merely parasitic on the new theory of scientific progress.

Kuhn’s alternative approach provided a much more satisfactory description of scientific progress at the expense of a decrease in the rigour and rationality of scientific methodology. On the other hand, the drawback of the philosophy of scientific revolutions was that it did not, and in a sense did not intend to, address issues related to the confirmation of hypotheses, scientific explanation and causation. In these areas, the traditional empiricistbased methodologies have yet to be replaced by more successful alternative views. The clash between the old scientific image and the ideas expressed by Kuhn is still going on within the philosophical community, albeit with less intensity than thirty years ago! However, the great majority of philosophers of science have been converted to the new ideas and capitalised on them. The result has been a host of alternative views including the sociology of science (Woolgar, Latour), modern pragmatism (Rorty), scientific anarchism (Feyerabend) and many others.

Further Reading

The Structure of Scientific Revolutions, T.S. Kuhn, Chicago Univ. Press, 1970 (2nd edition)
Representing and Intervening: Introductory Topics in the Philosophy of Natural Science, I. Hacking, Cambridge Univ. Press, 1983
What is this thing called Science?, A.F. Chalmers, Open University Press, 1992 (2nd edition)

Anastasios Economou is a lecturer in the Department of Instrumentation and Analytical Science at UMIST