Kathleen Nott's review was published in the TLS of February 27, 1959.

It is true (at least it is confirmed by the Encyclopaedia Britannica) that Bacon caught his death of cold through experimenting with antisepsis by refrigeration, having got out of his carriage on a bitter winter's day to stuff a fowl with snow. As well as being true this story sounds like a legend: and that, for didactic purposes, may be an advantage, for a myth or legend may fortify conviction where a relation of particular facts may vanish from memory or imagination. A myth speaks a universal language but speaks it in concrete terms which give the feeling of evidence. It is obvious, moreover, that Bacon's experiment was meant not only to prove something in particular – that cold preserves – but to illustrate the nature of proof in general. And thinking of this hardy experiment, we see, or think we see, that what scientists are trying to do before anything is to prove something, and that this is the kind of way in which they do it. This fortifies us in empirical faith. If a doubt crosses the mind of any of us that although we scrupulously observe all the conditions the bird may after all instantaneously decay, rather like Poe's M. Waldemar, we can trust the scientist to go out in the snow and stuff birds ad infinitum or "Until our faith is restored.

Though generally unanalysed, this is the vague and naive faith which laymen project upon scientists: and scientists who, outside their professional speciality, are often themselves naive, sometimes project it upon their own behaviour. Here there must be a qualification: philosophically naive is what is meant. Not all scientists study the philosophy of science, but this does not necessarily prevent them from knowing what they are doing: while those who have been too busy with science to read much philosophy have been known to give an account of their own activities as vivid and convincing as it is unconventional. A well-known biologist has been heard to say in public that he gets a " sort of hunch " and then collects a heap of facts and throws away those which seem not to fit it.

This might suggest that scientific, like poetic activity, to be properly grasped, must at least sometimes be seen from the inside. Logicians are not generally in this position of know-how. And they are not in fact in the scientific succession, however truly reverential the lip-service they pay to demonstration, to the high standard of scientific certainty. Their true philosophical forebears flourished before the days of empiricism, in the sense of experimentalism as we understand it. What was certain, "what amounted to proof, was what could be seen as self-evident, the tautologous, the analytical: what in short, with Descartes, could clearly be seen to be true. If this is made the standard, or if it remains the secret or unavowed standard of logical coherence, empirical evidence, the corroboration of the generalizations of a theory by the particular discoverable facts of experience, is seen to be difficult to justify logically. You may go on stuffing birds with snow for years. How are you to know beforehand, on what logical basis can you predict that, even if the same conditions are exactly fulfilled, a bird will not actually one day decay under your very nose ? In other words if there is no strictly logical principle of induction, how can you set yourself up as a scientist?

This is a philosophical problem which deserves the utmost respect as it has troubled philosophers as important as Bertrand Russell, and its implications have almost constructed a pattern of inquiry for the most prominent schools of contemporary epistemological thought, for these have been greatly influenced, if not dominated, by what they thought that scientists were doing. An important part of the answer to the problem is that scientists are doing something quite different, they are not actually competing with analytical or positivistic logicians.

Professor Karl Popper's Logik der Forschung, originally published in Vienna as far back as 1934, now makes a welcome appearance in translation. One cannot help feeling that if it had been translated as soon as it was originally published philosophy in this country might have been saved some detours. Professor Popper's thesis has that quality of greatness that, once seen, it appears simple and almost obvious. The book does something else which often goes with greatness or at least with the fruitfulness of a theory – boldly setting on its feet a variety of Weltanschauung which has been causing an unexplained discomfort by keeping some of us on our heads. A great claim, but then this is a remarkable book.

Professor Popper deals, then, with the problem of induction very simply: he shows that it does not exist: and a principle of induction is therefore a logician's dream. Scientists do not behave as Bacon thought – industriously gathering "countless grapes ripe .and in season" so that the wine of science may flow (or even industriously stuffing birds with snow). They work the other way round. They fling out hypotheses: and they test these, not prove them, by controlled and selective experiments. Science is the quest for truth, not the possession of it. It is also the challenge to refutation, it seeks not primarily the verification of its hypotheses but the kind of evidence which might falsify them. What Professor Popper is saying is that theories are not verifiable (in any sense which would satisfy a logical positivist). They use facts to test the predictions which they imply, but they do not originate in the expectation of final proof.

From Professor Popper's bold and simple conception there are consequences both general and particular far too many to enumerate. Among the particular ones is a new way of looking at the famous Heisenberg indeterminism, which saves a meaning for causality. Among the general ones is a fruitful demarcation between sciences and what Professor Popper has elsewhere called pseudo-sciences, particularly Freudianism and Marxism. It is a commonplace about both these systems that far from challenging "falsification," as Professor Popper would say, they endeavour to impose finality and they equate criticism with rationalized "resistance."

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