Kant And Science
by J.B.S Haldane

Immanuel Kant was born at Konisgberg on April 22, 1724. He is one of the least readable of the great philosophers, and except in Germany is little read by scientific men who have at least a nodding acquaintance with a Berkeley, a Lotze, or a Bergson. But it is the purpose of this article to suggest that not only are his philosophical views of extreme importance for science, but that they are more important now than when Kant arrived at them a hundred and fifty years since.

The highest compliment which posterity can pay any thinker is to regard his most original thoughts as the data of common sense. In our time this has happened to Descartes. The average man would probably agree with him that matter had extension and mind none. He would use Descartes' brilliant invention of co-ordinate geometry to illustrate an argument on unemployment or climate. He would be willing to regard his body as a machine guided to some extent by an unextended mind. The main reasons for the triumph of Cartesian philosophy have been the apparent explanation of such properties of matter as heat, colour, sound, and odour in terms of its configuration and motion. The progress of physics until twenty years ago had thoroughly justified Descartes' apparently arbitrary interest in the spatial properties of matter. And similarly physiology seemed to be progressing steadily towards an account of the body as a mechanism sometimes interfered with by a mind which could, however, for most purposes be left out of consideration. And whatever philosophical views one might subscribe to on religious or intellectual grounds, one tended to act over a large range of circumstances as if the above views were correct.

Except for Locke's distinction of primary and secondary qualities, very little post-Cartesian philosophy was incorporated into the assumptions of science, and the most recent work up to 1900, demanding, as it did, the postulation of an ether filling apparently empty space, bore a startlingly Cartesian appearance. In only one respect had any serious approach been made to the Kantian position. Mathematical physicists had quietly but definitely dropped the idea of causality; because they found that forces which have to be postulated as causes of motion do not possess those qualities of permanence which had rendered physical quantities such as mass, energy, and momentum so attractive. Of course, there were not wanting those who gave a more idealistic interpretation to the available evidence, but on the whole a realistic one seemed simplest. Then the theory of radiation broke down. It failed to explain radiation by very rapidly moving or very small bodies. The first failure led to the theory of relativity. According to this theory events form a four-dimensional manifold, and the relation between that series of events which constitutes our bodies and other series determines which of the latter we shall regard as simultaneous events, and which as successive and stationary. On Einstein's old theory the four-dimensional space-time was homogeneous, like the space and time of perception; and it was open to a philosopher who accepted his views to regard the action of the mind in perceiving space and time as merely selective, and not constitutive. But according to the general theory of relativity, which enabled Einstein to predict, among other things, the observed deflection of light by gravitation, space-time is not homogeneous, but bears a relation to the 'flat' space-time of the special theory similar to that between the surface of an orange and a plane. If this is accepted (and scientific men in general accept it, because it enables them to predict certain observable phenomena with accuracy), it is clear that the action of the mind in perceiving homogeneous space and time is truly constitutive, and it is dubious how far the space-like character of the event-manifold is not a mere concession to our ideas of what a 'real' world ought to be like. Eddington would go so far as to attribute every element in our experience of the external world, except that of atomicity, to our own mental processes, an interesting conclusion in view of Kant's insistence on the plurality of things in themselves.

The criticisms of the reality of space and time which arise from the theory of radiation by atoms are still more serious. The state of the atom before and after it radiates, and the subsequent history of its radiation, can be expressed in terms of the older physics, supplemented by relativity, with such accuracy that disagreements of less than one part in a thousand between theory and observation are the signal for a storm of further experiments. The probability of the passage of an atom from one stationary state to another, which coincides with the act of radiation or absorption, can also be dealt with by a mathematical theory due mainly to Planck and Bohr, and often with considerable accuracy. But every attempt to represent the process of radiation in terms of continuous space, time, or space-time, has broken down in the most hopeless manner. Bohr at least is convinced of the futility of any attempt at a 'model.' He is content to develop his beautiful, but highly formal, mathematical theory:

And write assured: In the beginning was the Deed

And so the world of physics reduces to a manifold of transcendental events, which the mind distributes in space and time, but by so doing creates a phenomenal world which is ultimately self-contradictory. And this is approximately the position reached by Kant in the Critique of Pure Reason.

In biology we are for the moment in a curiously Kantian position. The mechanistic interpretation has nowhere broken down in detail. Every process in the living organism which has been studied by physical and chemical methods has been found to obey the laws of physics and chemistry, as must obviously be the case if, as Kant taught, these laws merely represent the forms of our perception and abstract understanding. But these processes are co-ordinated in a way characteristic of the living organism. Thus we cannot avoid speaking of the function of the heart, as well as its mechanism. Some biologists cherish the pious hope that the physico-chemical explanation will be found to break down at some point; others the impious expectation that all apparently organic order will be reduced to physics and chemistry. There is very little in our present knowledge of biology to justify either of these standpoints, though evidence from other sources may seem to favour the former. The physiologist is therefore at present left in the peculiarly exasperating position reached by Kant in the second part of the Critique of Judgment. However mechanistic his standpoint, he must use the idea of adaptation at least as a heuristic principle. He will probably attempt to account for it as a result of natural selection, but natural selection is more fitted to explain the origin of given adaptations than the existence of living beings to which the term adaptation can be applied with a meaning. At present, with Kant, we are compelled to leave open the question 'whether in the unknown inner ground of nature the physical and teleological connection of the same things may not cohere in one principle; we only say that our reason cannot so unite them.'

It thus appears that the doctrines of both physics and biology have reached stages which are more easily reconcilable with Kant's metaphysics than with that of any other philosopher. I do not suggest that either a physicist or a biologist need be a Kantian if he adopts any metaphysics: I claim, however, that other metaphysical systems, though they may be preferable on other grounds, are all definitely harder to adapt to the present data of science. If, for example, with Russell in his Analysis of Mind, we regard perception as essentially a selection of certain sensa from a larger number which exist, we arrive at a real world vastly more complicated than that of physics, even though it finds no room for purpose. If, with J. S. Haldane, we regard purpose as more fundamental than mechanism, we have to look forward to a complete restatement of physics on teleological lines in the future, without being able to form any clear idea of how in detail this is possible.

I should be the last to suggest that the Kantian standpoint was any more final than the Cartesian. On the other hand, there seems to me to be little ground for supposing that after another two centuries of scientific research (the conduct of politicians suggests that they may not be continuous) the data of science, which will then presumably include much of psychology, will support one rather than another of several post-Kantian systems. And it looks as if Kant was at least correct when he claimed to have written the prolegomena to every future metaphysic.

The reason why Kant stands in this rather unique relation to scientific thought is probably that he was the last man to make contributions of fundamental importance both to natural science and to metaphysics. Apart from his work on meteorology and earthquakes, he was the first to put forward the nebular hypothesis, and to point out the importance of tidal friction in cosmogony. He therefore understood the nature of scientific thought in a manner which is entirely impossible to the mere student of science and its history, and was able to frame a metaphysical system which is as applicable to modern scientific developments as the mathematical system of Gauss. Until a first-rate scientific worker once more takes to philosophy we shall not see another Kant.

End of Kant And Science by J.B.S. Haldane