The Structure of Scientific Revolutions is undoubtedly one of the most important and controversial books on philosophy of science ever written. In it, Thomas Kuhn dismissed various traditional views of scientific progress: science did not proceed by the accumulation of facts, from which we derive general observations and laws (as Francis Bacon thought); it did not seek to confirm theories through empirical evidence (as the logical positivists argued); and nor did it progress by the falsification of hypotheses (as Karl Popper proposed). Inductive reasoning, empirical evidence and falsification all play a role – Kuhn was not denying that – but, for Kuhn, all such approaches ignored the role played in science by key innovations or ‘paradigms’ (as he christened them). So, Newton’s Principia was not just a huge step forward in physics, it was a new ‘paradigm’ or theoretical approach that marked a different way of seeing things, a new framework for the interpretation of ‘facts’. By applying the Newtonian paradigm, subsequent scientists were enabled to understand, predict and account for the behaviour of the physical world in a way that they could not have done previously. However, a new paradigm also introduced its own terms (or put a new slant on old ones), and advanced a new method and principles. More than simply adding to old knowledge, therefore, the Newtonian paradigm represented a revolution.
Having defined paradigm in this way – as those methods and principles embodied in an exemplary text or thinker – Kuhn shows how scientific ‘progress’ is not a matter of steady logical advancement, but takes place through a ‘paradigm shift’ between old and new theories which are, ultimately, ‘incommensurable’. The terms ‘mass’ or ‘motion’ would mean different things as they were used by Galileo, Newton or Einstein, and so the respective theories cannot be cashed out in terms of each other – they involve different commitments and assumptions, different theoretical entities and forces. Because of this, the movement from one paradigm to another bears some resemblance to religious conversion. One simply abandons ship when the old theory becomes unworkable and accepts something new. The old geocentric astronomy of Ptolemy was superseded by the heliocentrism of Copernicus and Galileo because of the increasing number of anomalies thrown up by new astronomical observations, which Copernicanism was better able to accommodate. But this was not the whole picture. It is true that, rather than abandon their theory, Ptolemaic astronomers persisted in simply tinkering with their system to make it fit new data, and that Copernicanism would eventually provide a simpler, more coherent system. But, initially at least, Copernicanism did not provide a problem-free alternative – and the same was true of Newtonian physics, Einsteinian relativity, and Darwinian evolution. The jump from one paradigm to another is often made when it is far from certain that the new paradigm is ‘right’. Commitment to a paradigm is therefore at least partly an expression of faith or an assertion of value.
In this manner, Kuhn presents scientific progress as a less than rational process, not one of logical inevitability. However, we might think of this shift in commitment to a paradigm as motivated by a hunch or a guess – we change theories through good scientific instinct that the old way is unworkable and a new one might bear more fruit. But the influence of ‘irrationality’ is also a central feature of Kuhn’s view of day-to-day scientific activity – what he termed ‘normal science’. In applying a paradigm, scientists aren’t concerned with upsetting the apple-cart, but rather to extend the shared insights as far as possible. As such, anomalies are often discounted, ignored, or accommodated by minor adjustments and exceptions – much as the Ptolemaic astronomers did. Here, Kuhn disagrees with Popper: scientific hypotheses aren’t always advanced to be falsified, but are frequently maintained or tweaked in the face of potential falsification. But this is necessary for science: we can’t have revolution everyday, for there would be no progress; we must give the new paradigm a chance.
In light of these views, Kuhn has been accused of characterising science as irrational, and of promoting a form of relativism – that each paradigm, being incommensurable with others, is no more ‘true’ or ‘false’ than its predecessors. However, Kuhn denied this, and we may see him rather as trying to give a more historically and sociologically accurate picture of scientific progress and of what science actually is (rather than the rose-tinted, rational ideal). This is certainly true, and his always well-informed observations regarding scientific practice give greater plausibility to his arguments. However, it’s also fair to say that, even if Kuhn himself is not relativist or anti-rational, his arguments certainly provide ammunition for those who are.
All in all, Structure is a great book. It is not always engaging or fascinating – Kuhn’s style is accessible but somewhat precise and unlively (compared, for instance, to that of Paul Feyerabend). It is, however, a hugely important work, and – given the tendency of more radical thinkers to misrepresent Kuhn’s views – one worth reading first hand.
This 50th anniversary edition includes an excellent introduction by Ian Hacking (who does write engagingly) and also Kuhn’s 1969 postscript where he responds to his critics.
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