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By Root 3251 0

the law of habit is itself a causal law. Therefore if we take Hume seriously we must say: Although in the past the sight of an apple has been conjoined with expectation of a certain kind of taste, there is no reason why it should continue to be so conjoined: perhaps the next time I see an apple I shall expect it to taste like roast beef. You may, at the moment, think this unlikely; but that is no reason for expecting that you will think it unlikely five minutes hence. If Hume's objective doctrine is right, we have no better reason for expectations in psychology than in the physical world. Hume's theory might be caricatured as follows: 'The proposition "A causes B" means "the impression of A causes the idea of B".' As a definition, this is not a happy effort.

We must therefore examine Hume's objective doctrine more closely. This doctrine has two parts: (1) When we say 'A causes B', all that we have a right to say is that, in past experience, A and B have frequently appeared together or in rapid succession, and no instance has been observed of A not followed or accompanied by B. (2) However many instances we may have observed of the conjunction of A and B, that gives no reason for expecting them to be conjoined on a future occasion, though it is a cause of this expectation, i.e. it has been frequently observed to be conjoined with such an expectation. These two parts of the doctrine may be stated as follows: (1) in causation there is no indefinable relation except conjunction or succession; (2) induction by simple enumeration is not a valid form of argument. Empiricists in general have accepted the first of these theses and rejected the second. When I say they have rejected the second, I mean that they have believed that, given a sufficiently vast accumulation of instances of a conjunction, the likelihood of the conjunction being found in the next instance will exceed a half; or, if they have not held exactly this, they have maintained some doctrine having similar consequences.

I do not wish, at the moment, to discuss induction, which is a large and difficult subject; for the moment, I am content to observe that, if the first half of Hume's doctrine is admitted, the rejection of induction makes all expectation as to the future irrational, even the expectation that we shall continue to feel expectations. I do not mean merely that our expectations may be mistaken; that, in any case, must be admitted. I mean that, taking even our firmest expectations, such as that the sun will rise tomorrow, there is not a shadow of reason, for supposing them more likely to be verified than not. With this proviso, I return to the meaning of 'cause'.

Those who disagree with Hume maintain that 'cause' is a specific relation, which entails invariable sequence, but is not entailed by it. To revert to the clocks of the Cartesians: two perfectly accurate chronometers might strike the hours one after the other invariably, without either being the cause of the other's striking. In general, those who take this view maintain that we can sometimes perceive causal relations, though in most cases we are obliged to infer them, more or less precariously, from constant conjunction. Let us see what arguments there are for and against Hume on this point.

Hume summarizes his argument as follows:

'I am sensible, that of all the paradoxes, which I have had, or shall hereafter have occasion to advance in the course of this treatise, the present one is the most violent, and that 'tis merely by dint of solid proof and reasoning I can ever hope it will have admission, and overcome the inveterate prejudices of mankind. Before we are reconcil'd to this doctrine, how often must we repeat to ourselves, that the simple view of any two objects or actions, however related, can never give us any idea of power, or of a connexion betwixt them: that this idea arises from a repetition of their union: that the repetition neither discovers nor causes anything in the objects, but has an influence only on the mind, by that customary transition it produces: that this customary transition