other men's conduct, that leads us to this conclusion, but a certain instinctive propensity to expect it, similar to that which he supposes dictates our reliance upon human testimony? One would think that, as in Newton's first law of motion, the mere absence of any motive to act otherwise would be a sufficient ground of such expectation. Not to say that to affirm of the same man, that from the same motive he can act differently, involves a contradiction of our notion of the operation of motives at all.

§ 21. Perhaps, as he understood it, this XIth Principle is only a case of the XIIth and last principle of contingent truth,-which is, that "in the phenomena of nature, what is to be, will probably be like to what has been under similar circumstances."

It cannot be, he observes, experience which gives us this persuasion, for all experience (meaning, I apprehend, all reasoning from experience) is grounded upon a belief that the future will be like the past. He adds, it is remarkable that though all our expectation of what is to happen in the course of nature is derived from the belief of this principle, yet no man, before Mr. Hume, ever thought of questioning the ground of this be

lief; which he admits that "that philosopher has shewn clearly and invincibly, to be grounded neither upon reasoning nor intuitive evidence;" it is not therefore, he says, a necessary truth.

§ 22. Mr. Hume's doctrine on this subject is to be found in the IVth Section of his Inquiry concerning human understanding. And as Dr. Reid has thus explicitly admitted the conclusiveness of his reasoning upon it, it may be worth while to consider it more particularly. In the first part of that section, he contents himself with shewing that all our reasonings concerning matter of fact, and real existence, are founded merely in the relation of cause to effect: and again, that the foundation of all our reasonings and conclusions concerning that relation, in particular instances, rests wholly upon experience. So far I am not aware that there was any thing new in Mr. Hume's doctrine. But he goes on to ask, in the 2nd part, what is the foundation of all our conclusions from experience itself?

If a body of like colour and consistency with that bread which we have formerly eaten, be presented to us, we make no scruple of repeating the experiment, and foresee with certainty, like nourishment and support. Now this,' says Mr. Hume,

'is a process of the mind or thought, of which I would willingly know the foundation. It is admitted on all hands, that there is no known connexion between the sensible qualities and secret powers; and as to past experience, it can be admitted to give direct and certain information of those precise objects only, and that precise period of time which fell under its cognizance.'

Mr. Hume proceeds to shew, that the consequence cannot be inferred by demonstrative reasoning, since it implies no contradiction, that the course of nature may change, or that an object, seemingly like those we have experienced, may be attended with different or contrary effects. Still less can it be derived as probable from our past experience, since the grounds of inference from past experience to the future, is, in fact, the very point in question.

His own solution of the difficulty is given in the following Section, in which he ascribes the phenomenon in question to the effect of custom or habit. Whenever,' says he, 'the repetition of any particular act or operation produces a propensity to renew the said act or operation, without being impelled by any reasoning or process of the understanding, we always say that this propensity is the effect of custom.' Accordingly, he after

wards adds, it is certain we advance here a very intelligible proposition, if not a true one, when we assert, that after the constant conjunction of two objects, heat and flame, for instance, weight and solidity, we are determined by custom alone, to expect from the one the appearance of the other *.'

$ 23. It is singular that Mr. Hume should not have observed the very palpable inconsistency of his doctrine here. Custom, according to his own definition, may beget a propensity to renew any act which we have often repeated, without being impelled by any process of the understanding, but this very statement supposes, that it was such a process of the understanding, and not

*Pascal, in one of his "Thoughts," has remarkably anticipated the expression of this doctrine of Mr. Hume's: "La coutume fait nos preuves les plus fortes. Elle incline les sens, qui entrainent l'esprit, sans qu'elle y pense. Qui a démontré qu'il sera demain jour et que nous mourrons, et qu'y-a-t-il de plus universellement cru? C'est donc la coutume qui nous en persuade."-Pensées, p. 63. A remarkable coincidence of doctrine between the most religious and most sceptical of modern philosophers. But in fact, in philosophy, Pascal was hardly less sceptical than Hume himself; and it was upon the uncertainty of all human grounds of knowledge, that he built the necessity of resorting to those of another and higher kind.

custom which originally suggested the act itself *. Mr Hume, in fact, has strangely confounded the repetition of the mere passive perception of the two objects as conjoined, with the act of the mind which, upon the perception of that repetition, connects them as cause and effect.

It is true, Mr. Hume's proposition here may, in one sense, be said to be (as he says) intelligible; because being determined by custom, may bear the sense of being determined by the observation of customary conjunction. But thus understood, it plainly would not serve Mr. Hume's purpose, which is to explain how it is that this observation of customary or constant conjunction hitherto, should lead the mind to expect its continuance in future. But if Mr. Hume meant, as obviously he must, to state that it is custom that leads the mind to expect the continuance of the customary connexion of phenomena, I must say, that his proposition is the very reverse of intelligible. At any rate, it is certainly not true. The case may be one in which we have never made the inference before. Suppose the concomitancy in question to

This remark has been made by the Author of the Quarterly Review of Mr. Stewart's second volume.-See Quarterly Review, Vol. XII. p. 311.