cient cause of vision, or the perception of the objects of sight. And if it were not intended by the Creator that this should be the process by which vision is effected, whence that exquisite structure of the organ itself, its appurtenances, its humours, its membranes, its muscles, and its whole form so wonderfully contrived to accomplish the great purpose for which it was intended? Would not all this wonderful array of parts; these curious contrivances and complicated machinery, appear to answer no important end, unless it was intended to be the instrument of vision? If mind alone can act in vision as an efficient cause, and matter be so utterly unimportant, why would not any lump of dead, unorganised matter have answered the purpose as well as such a nicely adjusted optical instrument?

But since Dr. Reid denies, that the several media which act upon the senses, and through them upon the mind, are the efficient causes of perception; let us put to him the inquiry what is the efficient cause? Mind, he would say-What, then, has matter to do in the affair? "It acts," says he, "only as an occasional cause." Thus we are plunged at once into the dark profound of the theory of Mallebranche, where our faculties are lost and absorbed in an impenetrable mysticism. An occasional cause, which possesses no power to produce its effect, is a non-descript kind of thing, which no one has ever yet been able to render intelligible, or ever will be able. But as Mr. Locke has before, in an extract which we took from him, sufficiently exposed the folly and absurdity of the doctrine of occasional causes, we forbear indulging ourselves in any further reflections upon the subject.

The next objection urged by Dr. Reid against the doctrine of Mr. Locke, which we have before stated, is in the following terms."Another conclusion very generally made by philosophers, is, that in perception, an impression is made upon the mind, as well as upon the organ, nerves and brain. Aristotle thought, that the form or image of the object perceived,

enters by the organ of sense, and strikes upon the mind. Mr. Hume gives the name of impressions to all our perceptions, to all our sensations, and even to the objects which we perceive. Mr. Locke affirms very positively, that the ideas of external objects are produced in our minds by impulse, "that being the only way we can conceive bodies to operate in. It ought, however, to be observed in justice to Mr. Locke, that he retracted this notion in his first letter to the Bishop of Worcester, and promised, in the next edition of his essay, to have that passage rectified; but, either from forgetfulness in the author, or negligence in the printer, the passage remains in all the subsequent editions I have seen." In answer to these allegations, we deny the fact, that Mr. Locke, Aristotle, or any of the best philosophers maintained, that in perception, an impression is made upon the mind as well as upon the organ and brain, in the sense in which that doctrine is attributed to them. We shall afterwards have occasion to show, that Aristotle held no such absurd opinion as is here ascribed to him; that the image of the object perceived enters by the organ of sense and strikes upon the mind. Such a crude and ridiculous notion could never have entered into so clear a head as that of the Greek philosopher; but was a child that sprang naturally from the loins of his miserable interpreters and falsifiers, the fraternity of schoolmen. When Dr. Reid affirms, that Mr. Locke positively maintains, that the ideas of external objects are produced in our minds by impulse, that being the only way we can conceive bodies to operate in; it shows how extremely careless he is, in his references to that author, and how indifferent to the ascertaining of his true opinions. If he had recurred to the passage of Mr. Locke, and had possessed any of that candour and liberality which is the true spirit of philosophy, he could not but have perceived that, in the paragraph quoted from him, he is speaking, not of any action produced upon the mind by outward objects, but of the impression

made by them upon the organs of sense. He is inculcating there, the very same doctrine held by Aristotle in regard to the operation of the qualities of bodies upon the senses, in which they are said to make impressions upon them as a seal does upon wax. Hear Mr. Locke himself" The next thing to be considered, is; how bodies produce ideas in us, and that is manifestly by impulse, the only way we can conceive bodies to operate in. If, then, external objects be not united to our mind, when they produce ideas in it, and yet we perceive these original qualities in such of them as singly fall under our senses; it is evident, that some motion must be thence continued by our nerves or animal spirits, by some parts of our bodies, to the brain or seat of sensation, there to produce in our minds the particular ideas we have of them." We see, therefore, that the doctrine here held by Mr. Locke, is, that bodies through the instrumentality of their several media act upon the senses, and occasion certain motions in the nerves and brain, that become the cause of ideas in the mind; but he does not say that they make any impression upon the mind, such as that which they make upon the organs of sense. We shall presently see, that so far is he from attempting to explain in what manner any motions in the brain can produce ideas in the mind, or from maintaining, that matter can act upon mind only by impulse, he expressly denies that the process of perception can be explained, by any powers or capacities with which we are endowed, and is resolvable solely into the will and power of God. It is true, that in one of his letters to the Bishop of Worcester, he afterwards expressed some distrust of the opinion he here advanced, viz. that bodies could act upon each other (not upon mind) only by impulse; but instead of ascribing the insertions of this passage in the future editions of his works, to negligence in the printer or forgetfulness in an author, who discovered on all occasions such an ardent pursuit of truth and so much readiness and alacrity to make alterations in his

treatise, upon any change in his opinions; I would rather attribute it to what was a more probable, and I suspect the true reason; a conviction, upon further reflection and examination, that there was no sufficient cause to induce him to alter his language, or give up his doctrine. Mr. Locke, in the letter referred to, appears, at that moment to have thought, that Sir Isaac Newton, in his Principia, had proved, upon the principles of his system of gravitation, in which the heavenly bodies are said to tend towards each other according to certain laws, that one portion of matter may act upon another without impulse, and even through a vacuum. But upon a more minute inquiry, he may have perceived that Newton maintained no such opinion, and expressly denies, that he supposes the heavenly bodies to operate upon each other through a vacuum. He himself, obviously supposes, that the attraction of bodies is occasioned by some thin and elastic fluid pervading the solar system, and propelling them towards each other by impulse; although he declares that he could not deduce the existence of such a principle from the phenomena exhibited to him, but only the laws of its action. This is a much more probable account of Mr. Locke's failure to comply with the promise, which he made to the Bishop of Worcester, in regard to a proposed alteration of his work, than that which has been given by Dr. Reid. He found no sufficient reason, upon examination, to alter his language, or relinquish his opinions.

It is not denied, that Mr. Locke often makes use of the term, impressions made upon the mind, but he uses it only in the popular and figurative sense, as implying some effect produced uponit by the agency of the body, which Dr. Reid himself allows to be a mode of expression authorised by ordinary usage. But, that he is liable to the charge laid against him in the following passage, we utterly deny. "But it is evident," says Dr. Reid " from the manner in which the phrase, (impressions) is used by modern Philosophers, they mean not barely to express by it, my perceiving an object, but to

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explain the manner of perception. They think that the object perceived acts upon the mind in some way similar to that in which one body acts upon another, by making an impression upon it. The impression upon the mind is conceived to be something, wherein the mind is altogether passive, and has some effect produced in it by the object. But this is an hypothesis, which contradicts the common sense of mankind, and ought not to be admitted without proof. When I look upon the wall of my room, the wall does not act at all, nor is capable of acting; the perceiving it is an act or operation in me." This last sentence is indeed very extraordinary, as coming from one who had so well studied the subject of metaphysicks; and discovers at times no inconsiderable acuteness and profoundness of observation. It would appear to be rather the crude suggestion of one who was totally unskilled in the science. When I look at the wall of my room; who was ever silly enough to assert, that the wall acts upon my mind, or even upon my organs of sense. The schoolmen, indeed, misinterpreting Aristotle, ascribed to him the opinion, that sensible species or films passed off from the object, and impinging upon the senses made their way into the mind, and enabled us to perceive. But even this doctrine, absurd and ridiculous as it is, did not suppose any action of the object contemplated, except through the intervention of their several media, and those aerial beings called sensible species. The account given of vision is very simple and intelligible, according to the system of Mr. Locke and Aristotle. When I look at the wall of my room; they do not say that the wall acts upon my mind or sense, but that the rays of light reflected from it, pass into the eye, an optical instrument, adapted to the purpose of collecting and refracting them, and forming an image upon the retina, cause such motions in the nervous coat connected with the brain, and in the brain itself, as to enable the mind to have a perception of it. In what way this action, in the bodily organs,