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HIS SCEPTICISM AS TO THE SENSES. 631
abstract, or thoroughgoing philosophy of scepticism, will render it unnecessary for us to follow our author minutely through the different branches of this inquiry. Overlooking, or at least undervaluing the indisputable fact, that our sensations are uniformly accompanied with a distinct apprehension, and firm belief in the existence of real external objects, he endeavours to prove, that the qualities which we ascribe to them are in reality nothing more than names for our peculiar sensations; and maintains accordingly, that because men differ in their opinions of the same object, it is impossible to suppose that they actually perceive any real object at all; as a real existence must always appear the same to those who actually perceive it.
His illustrations are of this nature. Water, which feels tepid to a Laplander, would appear cold to a native of Sumatra: But the same water cannot be both hot and cold: therefore it is to be inferred that neither of them is affected by any real quality in the external body, but that each describes merely his own sensations. Now, the conclusion here is plainly altogether unwarranted by the fact; since it is quite certain that both the persons in question perceive the same quality in the water, though they are affected by it in a different manner. The solution of the whole puzzle is, that heat and cold are not different qualities ; but different degrees of the same quality, and probably exist only relatively to each other. If the water is of a higher temperature than the air, or the body of the person who touches it, he will call it warm ; if of a lower temperature, he will call it cold. But this does not prove by any means, that the difference between two distinct temperatures is ideal, or that it is not always perceived by all indivi duals in the very same way. If Mr. Drummond could find out a person who not only thought the water cold which other people called warm, but also thought that warm which they perceived to be cold, he might have some foundation for his inference; but while all man kind agree that ice is cold, and steam hot, and concur indeed most exactly in their judgments of the
ILLUSTRATIONS WEAKLY SUPPORTED.
comparative heat of all external bodies, it is plainly a mere quibble on the convertible nature of these qualities, to call in question the identity of their perceptions, because they make the variable standard of their own temperature the rule for denominating other bodies hot or cold.
In the same way, Mr. Drummond goes on to say, one man calls the flavour of assafætida nauseous, and another thinks it agreeable; - one nation delights in a species of food which to its neighbours appears disgusting. How, then, can we suppose that they perceive the same real qualities, when their judgments in regard to them are so diametrically opposite ? Now, nothing, we conceive, is more obvious than the fallacy of this reasoning. The liking, or disliking, of men to a particular object, has nothing to do with the perception of its external qualities; and they may differentirely as to their opinion of its agreeableness, though they concur perfectly as to the description of all its properties. One man may admire a tall woman, and another a short one; but it would be rather rash to infer, that they did not agree in recognising a difference in stature, or that they had no uniform ideas of magnitude in general. In the same way, one person may have an antipathy to salt, and another a liking for it; but they both perceive it to be salt, and both agree in describing it by that appellation. To give any degree of plausibility to Mr. Drummond's inferences, it would be necessary for him to show that some men thought brandy and Cayenne pepper insipid and tasteless, and objected at the same time to milk and spring water as excessively acrid and pungent.
In the concluding part of his book, Mr. Drummond undertakes nothing less than a defence of the theory of Ideas, against the arguments of Dr. Reid. This is a bold attempt; but, we are inclined to think, not a suc
Mr. Drummond begins with the old axiom, that nothing can act but where it is; and infers, that as real material objects cannot penetrate to the seat of the soul, that sentient principle can only perceive certain images or ideas of them; against the assumption of which
MISTAKES AS TO THEORY OF IDEAS.
he conceives there can be no considerable obstacle. Now, it is needless, we think, to investigate the legitimacy of this reasoning very narrowly, because the foundation, we are persuaded, is unsound. The axiom, we believe, is now admitted to be fallacious (in the sense at least here assigned to it) by all who have recently paid any attention to the subject. But what does Mr. Drummond understand exactly by ideas ! Does he mean certain films, shadows, or simulacra, proceeding from real external existences, and passing through real external organs to the local habitation of the soul? If he means this, then he admits the existence of a material world as clearly as Dr. Reid does; and subjects himself to all the ridicule which he has himself so justly bestowed upon the hypothesis of animal spirits, or any other supposition, which explains the intercourse between mind and matter, by imagining some matter, of so fine a nature as almost to graduate into mind! If, on the other hand, by ideas, Mr. Drummond really means nothing but sensations and perceptions (as we have already explained that word), it is quite obvious that Dr. Reid has never called their existence in question; and the whole debate comes back to the presumptions for the existence of an external world ; or the reasonableness of trusting to that indestructible belief which certainly accompanies those sensations, as evidence of their having certain external causes. We cannot help doubting, whether Mr. Drummond has clearly stated to himself, in which of these two senses he proposes to defend the doctrine of ideas. The doctrine of IMAGES proceeding from actual external existences, is the only one in behalf of which he can claim the support of the ancient philosophers; and it is to it he seems to allude, in several of the remarks which he makes on the illusions of sight. On the other supposition, however, he has no occasion to dispute with Dr. Reid about the existence of ideas; for the Doctor assuredly did not deny that we had sensations and perceptions, notions, recollections, and all the other affections of mind to which the word idea may be applied, in that
PLAIN FALLACY OF HUME'S ILLUSTRATION.
other sense of it. There can be no question upon that supposition, but about the origin of these ideas — which belongs to another chapter.
Mr. Drummond seems to lay the whole stress of his argument upon a position of Hume’s, which he applies himself to vindicate from the objections which Dr. Reid has urged against it. “The table which I see," says Mr. Hume, “diminishes as I remove from it; but the real table suffers no alteration:- it could be nothing but its image, therefore, which was present to my mind.” Now this statement, we think, admits pretty explicitly, that there is a real table, the image of which is presented to the mind: but, at all events, we conceive that the phenomenon may be easily reconciled with the supposition of its real existence. Dr. Reid's error, if there be one, seems to consist in his having asserted positively, and without any qualification, that it is the real table which we perceive, when our eyes are turned towards it. When the matter however is considered very strictly, it will be found that by the sense of seeing we can perceive nothing but light, variously arranged and diversified; and that, when we look towards a table, we do not actually see the table itself, but only the rays of light which are reflected from it to the eye. Independently of the cooperation of our other senses, it seems generally to be admitted, that we should perceive nothing by seeing but an assemblage of colours, divided by different lines; and our only visual notion of the table (however real it might be) would, therefore, be that of a definite portion of light, distinguished by its colour from the other portions that were perceived at the same time. It seems equally impossible to dispute, however, that we should receive from this impression the belief and conception of an external existence, and that we should have the very same evidence for its reality, as for that of the objects of our other senses.
But if the external existence of light be admitted, a very slight attention to its laws and properties, will show how its appearances must vary, according to our distance from the solid objects which emit it. We perceive the form of bodies by sight, in short, very
WHAT WE TRULY KNOW BY SIGHT.
nearly as a blind man perceives them, by tracing their extremities with his stick: It is only the light in one case, and the stick in the other, that is properly felt or perceived; but the real form of the object is indicated, in both cases, by the state and disposition of the medium which connects it with our sensations. It is by intimations formerly received from the sense of Touch, no doubt, that we ultimately discover that the rays of light which strike our eyes with the impressions of form and colour, proceed from distant objects, which are solid and extended in three dimensions; and it is only by recollecting what we have learned from this sense, that we are enabled to conceive them as endued with these qualities. By the eye itself we do not perceive these qualities : nor, in strictness of speech, do we perceive, by this sense, any qualities whatever of the reflecting object; we perceive merely the light which it reflects; distinguished by its colour from the other light that falls on the eye along with it, and assuming a new form and extension, according as the distance or position of the body is varied in regard to us. These variations are clearly explained by the known properties of light, as ascertained by experiment; and evidently afford no ground for supposing any alteration in the object which emits it, or for throwing any doubts upon the real existence of such an object. Because the divergence of the rays of light varies with the distance between their origin and the eye, is there the slightest reason for pretending, that the magnitude of the object from which they proceed must be held to have varied also ?