Lectures on the Philosophy of the Human Mind (Vol. 1 of 3)

by Thomas Brown

“Clear as a beautiful transparent skin,

Which never hides the blood, yet holds it in;

Like a delicious stream it ever ran

As smooth as woman, and as strong as man.”[98]

The opinions of Hobbes, on the subject which we are considering, are stated at length, in that part of his Elements of Philosophy, which he has entitled Physica; and, far from justifying Dr Reid's assertion, with respect to the general ideal system of philosophers, may be considered, in this important respect, as far, at least, as relates to the unity of the idea, and the perception itself, as similar to his own. Sensation or perception, he traces to the impulse of external objects, producing a motion along the nerves towards the brain, and a consequent reaction outwards, which he seems to think, very falsely indeed, may account for the reference to the object as external. This hypothesis, however, is of no consequence. The only important point in reference to the supposed universality of the system of ideas, is whether this philosopher of another age, asserted the existence of ideas, as intermediate things, distinct from the mere perception; and, on this subject, he is as explicit as Dr Reid himself could be. The idea or phantasma, as he terms it, is the very perception or actus sentiendi. “Phantasma enim est sentiendi actus; neque differt a sensione, aliter quam fieri differt a factum esse.”[99] The same doctrine, and I may add also, the same expression of the unity of the actus sentiendi and the phantasma, are to be found in various other parts of his works.

I may, however, proceed still further back, to an author of yet wider and more varied genius, one of those extraordinary men whom nature gives to the world, for her mightiest purposes, when she wishes to change the aspect, not of a single science merely, but of all that can be known by man; that illustrious rebel, who, in overthrowing the authority of Aristotle, seemed to have acquired, as it were by right of conquest, a sway in philosophy, as absolute, though not so lasting, as that of the Grecian despot. “Time,” says one of the most eloquent of his countrymen, “has destroyed the opinions of Des Cartes. But his glory subsists still. He appears like one of those dethroned monarchs, who, on the very ruins of their empire, still seem born for the sovereignty of mankind.”

On the opinions of Des Cartes, with respect to perception, Dr Reid has dwelt at great length, and has not merely represented him as joining in that belief of ideas, distinct from perception, which he represents as the universal belief of philosophers, but has even expressed astonishment, that Des Cartes, whose general opinions might have led him to a different conclusion, should yet have joined in the common one. “The system of Des Cartes,” he says, “is with great perspicuity and acuteness explained by himself, in his writings, which ought to be consulted by those who would understand it.”[100] He probably was not aware, when he wrote these few lines, how important was the reference which he made, especially to those whom he was addressing; since, the more they studied the view which he has given of the opinions of Des Cartes, the more necessary would it become for them to consult the original author.

“It is to be observed,” he says, “that Des Cartes rejected a part only of the ancient theory, concerning the perception of external objects by the senses, and that he adopted the other part. That theory may be divided into two parts,—the first, that images, species, or forms of external objects, come from the object, and enter by the avenues of the senses to the mind; the second part is, that the external object itself is not perceived, but only the species or image of it in the mind. The first part Des Cartes and his followers rejected, and refuted by solid arguments; but the second part, neither he nor his followers have thought of calling in question; being persuaded that it is only a representative image, in the mind, of the external object that we perceive, and not the object itself. And this image, which the Peripatetics called a species, he calls an idea, changing the name only, while he admits the thing.”[101]—“Des Cartes, according to the spirit of his own philosophy, ought to have doubted of both parts of the Peripatetic hypothesis, or to have given his reasons, why he adopted one part, as well as why he rejected the other part; especially since the unlearned, who have the faculty of perceiving objects by their senses, in no less perfection than philosophers, and should therefore know, as well as they, what it is they perceive, have been unanimous in this, that the objects they perceive are not ideas in their own minds, but things external. It might have been expected, that a philosopher, who was so cautious as not to take his own existence for granted, without proof, would not have taken it for granted, without proof, that every thing he perceived was only ideas in his own mind.”[102]

All this might certainly have been expected, as Dr Reid says, if the truth had not been, that the opinions of Des Cartes are precisely opposite to the representation which he has given of them,—that, far from believing in the existence of images of external objects, as the immediate causes or antecedents of perception, he strenuously contends against them. The presence of the external body,—the organic change, which he conceives to be a sort of motion of the small febrils of the nerves and brain,—and the affection of the mind, which he expressly asserts to have no resemblance whatever to the motion that gave occasion to it,—these are all which he conceives to constitute the process of perception, without any idea, as a thing distinct,—a fourth thing intervening between the organic and the mental change. And this process is exactly the process which Dr Reid himself supposes, with this only difference,—an unimportant one for the present argument,—that Dr Reid, though he admits some intervening organic change, does not state, positively, what he conceives to be its nature, while the French philosopher supposes it to consist in a motion of the nervous fibrils. The doctrine of Des Cartes is to be found, very fully stated, in his Principia Philosophiæ, in his Dioptrics, and in many passages of his small controversial works. He not merely rejects the Peripatetic notion, of images or shadowy films, the resemblance of external things, received by the senses,—contending, that the mere organic affection—the motion of the nervous fibril—is sufficient, without any such images, “diversos motus tenuium uniuscujusque nervi capillamentorum sufficere ad diversos sensus producendum;” and proving this by a very apposite case, to which he frequently recurs, of a blind man determining the dimensions of bodies by comprehending them within two crossed sticks,—in which case, he says, it cannot be supposed, that the sticks transmit, through themselves, any images of the body; but he even proceeds to account for the common prejudice, with respect to the use of images of perception, ascribing it to the well-known effect of pictures in exciting notions of the objects pictured. “Such is the nature of the mind,” he says, “that, by its very constitution, when certain bodily motions take place, certain thoughts immediately arise, that have no resemblance whatever, as images, to the motions in consequence of which they arise. The thoughts which words, written or spoken, excite, have surely no resemblance to the words themselves. A slight change in the motion of a pen may produce, in the reader, affections of mind the most opposite; nor is it any reply to this to say, that the characters traced by the pen are only occasions, that excite the mind itself to form opposite images,—for the case is equally striking, when no such image can be formed, and the feeling is the immediate result of the application of the external body. When a sword has pierced any part, is not the feeling excited as different altogether from the mere motion of the sword, as colour, or sound, or smell, or taste; and since we are sure, in the case of the mere pain from the sword, that no image of the sword is necessary, ought we not to extend the same inference, by analogy, to all the other affections of our senses, and to believe these also to depend, not on any images, or things transmitted to the brain, but on the mere constitution of our nature, by which certain thoughts are made to arise, in consequence of certain corporeal motions?” The passage is long, indeed, but it is so clear, and so decisive, as to the misrepresentation by Dr Reid of the opinion which he strangely considered himself as confuting, that I cannot refrain from quoting the original, that you may judge for yourselves, of the real meaning, which a translation might be supposed to have erred in conveying.