Published online by Cambridge University Press: 14 March 2022
This essay is a refutation of Hume on causal inference. The decisive point of the refutation is that Hume's argument is invalid unless it is assumed, contrary to his own relational theory of time, that mere difference in dates can affect the course of nature. In the preliminary discussion of sections II and III the words “cause,” “effect,” and “causal relation” are employed in a nontechnical sense, which is exemplified in such statements as “Fire causes heat”, “Lightning and thunder are causally related”, “When one turns the steering wheel to the right, the effect is that the car moves to the right”, and so on. But in order to forestall rebuttals in defense of Hume one needs a greater precision in terminology as well as in conception of causality. Section IV aiming at precision gives a statement of the principles of causality which is in accordance with the position of modern science. An examination of this statement shows that the validity of causal inference must be accepted along with a relational theory of time. A comment on causal inference in relation to induction brings the discussion to a close.
1 Of course, according to Hume, some impression must be the original of the idea of necessary connection. His point is that this impression is not sensory but an internal feeling of expectation or belief generated by a habit of associating events which have always been observed to occur in a sequence.
2 Enquiry Concerning Human Understanding, I, 4, p. 37ff., Clarendon Press, 1894.
3 A Treatise of Human Nature, I, ii, 3, p. 36, Clarendon Press, 1896.
4 B. Russell, Our Knowledge of the External World, N. Y., W. Norton & Co., 1929, p. 232.
5 It is unnecessary for the purpose of this discussion to take into consideration other mathematical forms used in the theories of physics other than classical mechanics.
6 D'Abro, The Decline of Mechanism, N. Y., D. Van Nostrand Co., 1939, p. 179.
7 A law of motion would not be applicable to a system whose initial state was not specifiable. To specify a state of a mechanical system, a simultaneous determination of the positions and velocities of the constituent-patricles is required. Since a simultaneous determination of the position and momentum of an electron is impossible, a mechanical law cannot be applied and its motion cannot be predicted.
8 Cf. R. Lindsay and H. Margenau, Foundations of Physics, N. Y., J. Wiley & Sons, 1936, Ch. X.
For an entirely non-technical explanation of the point cf. L. Silberstein, Casuality, Macmillan & Co., London, 1933, pp. 53 ff.
9 Ibid., p. 241.