deed, if we take for granted, that in perception the mind acts upon the object, or the object upon the mind, and, at the same time, adinit the truth of the maxim, that "nothing can act but where it is," we must, of necessity, conclude, either that objects are perceived in a way similar to what is supposed in the ideal theory, or that, in every act of perception, the soul quits the body, and is present to the object perceived. And accordingly, this alternative is expressly stated by Malebranche; who differs, however, from the writer last quoted. in the choice which he makes of his hypothesis, and even rests his proof of its truth on the improbability of the other opinion. "I suppose," says he, " that every "one will grant, that we perceive not external objects immediately, "and of themselves. We see the sun, the stars, and an infinity of ob"jects without us; and it is not at all likely that, upon such occasions, "the soul sallies out of the body, in order to be present to the objects "perceived. She sees them not therefore by themselves and the im"mediate object of the mind is not the thing perceived, but something "which is intimately united to the soul; and it is that which I call an "idea so that by the word idea, I understand nothing else here but "that which is nearest to the mind when we perceive any object.-It ought to be carefully observed, that, in order to the mind's perceiving "any object, it is absolutely necessary that the idea of that object be "actually present to it. Of this it is not possible to doubt. The << things which the soul perceives are of two kinds. They are either "in the soul, or they are without the soul. Those that are in the soul, "are its own thoughts; that is to say, all its different modifications. "The soul has no need of ideas for perceiving these things. But with "regard to things without the soul, we cannot perceive them but by "means of ideas."

To these quotations, I shall add another, which contains the opinion of Buffon upon the subject. As I do not understand it so completely, as to be able to translate it in a manner intelligible to myself, I shall transcribe it in the words of the author.

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"L'ame s'uni intimement à tel objet qu'il lui plâit, la distance, la "grandeur, la figure, rien ne peut nuire à cette union lorsque l'ame la "vent: elle se fait et se fait en un instant. . . . la volonté n'est elle "donc qu'un mouvement corporel, et la contemplation un simple at"touchement ? Comment cet attouchement pourroit il se faire sur un objet éloigné, sur un sujet abstrait? Comment pourroit il s'opérer en un instant indivisible? A-t-ou jamais concu du mouvement, sans qu'il "yêut de l'espace et du tems? La volonté, si c'est un mouvement, "n'est donc pas un mouvement matériel, et si l'union de l'ame à son · "objet est un attouchement, un contact, cet attouchement ne se fait il pas au loin? ce contact n'est il pas une pénétration ?"

All these theories appear to me to have taken rise, first, from an inattention to the proper object of philosophy, and an application of the same general maxims to physical and to efficient causes; and secondly, from an apprehension, that we understand the connexion between impulse and motion, better than any other physical fact. From the detail which I have given, it appears how extensive an influence this prejudice has had on the inquiries both of natural philosophers and of metaphysicians.

In the foregoing reasonings, I have taken for granted, that motion

may be produced by impulse; and have contented myself with asserting, that this fact is not more explicable, than the motions which the Newtonians refer to gravitation; or than the intercourse which is carried on between the mind and external objects in the case of perception. The truth, however, is, that some of the ablest philosophers in Europe are now satisfied, not only that there is no evidence of motion being in any case produced by the actual contact of two bodies: but that very strong proofs may be given of the absolute impossibility of such a supposition; and hence they have been led to conclude, that all the effects, which are commonly referred, to impulse, arise from a power of repulsion, extending to a small and imperceptible distance round every element of matter. If this doctrine shall be confirmed by future speculations in physics, it must appear to be a curious circumstance in the history of science, that philosophers have been so long occupied in attempting to trace all the phenomena of matter, and even some of the phenomena of mind, to a general fact, which, upon an accurate examination, is found to have no existence.-I do not make this observation with a view to depreciate the labours of these philosophers: for, although the system of Boscovich were completely established, it would not diminish in the smallest degree, the value of those physical inquiries, which have proceeded on the common hypothesis, with respect to impulse. The laws which regulate the communication of motion, in the case of apparent contact, are the most general facts we observe among the terrestrial phenomena; and they are, of all physical events, those which are the most familiar to us from our earliest infancy. It was therefore not only natural but proper, that philosophers should begin their physical inquiries, with attempting to refer to these, (which are the most general laws of nature, exposed to the examination of our senses,) the particular appearances they wished to explain. And if ever the theory of Boscoviah should be completely established, it will have no other effect, than to resolve these laws into some principle still more general, without effecting the solidity of the common doctrine, so far as it goes.

SECTION III.

Of Dr. Reid's Speculations on the Subject of Perception.

It was chiefly in consequence of the sceptical conclusions which Bishop Berkeley and Mr. Hume had deduced from the ancient theories of perception, that Dr. Reid was led to call them in question; and he appears to me to have shewn, in the most satisfactory manner not only that they are perfectly hypothetical, but that the suppositions, they involve, are absurd and impossible. His reasonings, on this part of our constitution, undoubtedly form the most important accession which the philosophy of the human mind has received since the time of Mr. Locke.

But although Dr. Reid has been at much pains to everturn the old ideal system, he has not ventured to substitute any hypothesis of his own in its place. And, indeed, he was too well acquainted with the limits prescribed to our philosophica. inquiries, to think of indulging his curiosity in such unprofitable speculations. All, therefore that he is to be understood as aiming at, in his inquiries concerning our perceptive

powers, is, to give a precise state of the fact, divested of all theoretical expressions; in order to prevent philosophers from imposing on themselves any longer, by words without meaning, and to extort from them an acknowledgment, that, with respect to the process of nature in perception, they are no less ignorant than the vulgar.

According to this view of Dr. Reid's reasonings on the subject of perception, the purpose to which they are subservient may appear to some to be of no very considerable importance; but the truth is, that one of the most valuable effects of genuine philosophy, is to remind us of the limited powers of the human understanding, and to revive those natural feelings of wonder and admiration at the spectacle of the universe, which are apt to languish in consequence of long familiarity. The most profound discoveries which are placed within the reach of our researches lead to a confession of human ignorance; for, while they flatter the pride of man, and increase his power by enabling him to trace the simple and beautiful laws by which physical events are regulated, they call his attention, at the same time, to those general and ultimate facts which bound the narrow circle of his knowledge; and which, by evincing to him the operation of powers, whose nature must for ever remain unknown, serve to remind him of the insufficiency of his faculties to penetrate the secrets of the universe. Wherever we direct our inquiries; whether to the anatomy and physiology of animals, to the growth of vegetables, to the chemical attractions and repulsions, or the motions of the heavenly bodies, we perpetually perceive the effects of powers which cannot belong to matter. To a certain length we are able to proceed; but in every research, we meet with a line, which no industry nor ingenuity can pass It is a line too, which is marked with sufficient distinctness, and which no man now thinks of passing, who has just views of the nature and object of philosophy. It forms the separation between that field which falls under the survey of the physical inquirer, and that unknown region, of which, though it was necessary that we should be assured of the existence, in order to lay a foundation for the doctrines of natural theology, it hath not pleased the Author of the universe to reveal to us the wonders, in this infant state of our being. It was, in fact, chiefly by tracing out this line, that Lord Bacon did so much service to science.

Besides this effect, which is conimon to all our philosophical pursuits of impressing the mind with a sense of that mysterious agency, or efficiency, into which general laws must be resolved, they have a tendency, in many cases, to counteract the influence of habit, in weakening those emotions of wonder and of curiosity, which the appearances of nature are so admirably fitted to excite. For this purpose, it is necessary, either to lead the attention to facts which are calculated to strike by their novelty, or to present familiar appearances in a new light; and such are the obvious effects of philosophical inquiries; sometimes extending our views to objects which are removed from vulgar observation, and sometimes correcting our first apprehensions with respect to ordinary events.-The communication of motion by impulse, (as I already hinted,) is as unaccountable as any phenomenon we know; and yet, most men are disposed to consider it as a fact which does not re sult from will, but from necessity. To such men, it may be useful to direct their attention to the universal law of gravitation ; which, although

not more wonderful in itself, than the common effects of impulse is more fitted, by its novelty, to awaken their attention, and to excite their curiosity. If the theory of Boscovich should ever be established on a satisfactory foundation, it would have this tendency in a still more remarkable degree, by teaching us that the communication of motion by impulse, (which we are apt to consider as a necessary truth,) has no existence whatever; and that every case in which it appears to our senses to take place, is a phenomenon no less inexplicable, than that principle of attraction which binds together the most remote parts of

the universe.

If such, however, be the effects of our philosophical pursuits when successfully conducted, it must be confessed that the tendency of imperfect or erroneous theories is widely different. By a specious solution of insuperable difficulties, they so dazzle aud bewilder the understanding, as, at once, to prevent us from advancing, with steadiness, towards the limit of human knowledge, and from perceiving the existence of a re gion beyond it, into which philosophy is not permitted to enter In such cases, it is the business of genuine science to unmask the imposture, and to point out clearly both to the learned and to the vulgar, what reason can, and what she cannot, accomplish. This, I apprehend, has been done, with respect to the history of our perceptions, in the most satisfactory manner, by Dr. Reid.-When a person little accustomed to metaphysical speculations is told, that, in the case of volition, there are certain invisible fluids, propagated from the mind to the organ which is moved; and that, in the case of perception, the existence and qualities of the external object are made known to us by means of species, or phantasms, or itnages, which are present to the mind in the sensorium; he is apt to conclude that the intercourse between mind and matter is much less mysterious than he had supposed; and that, although these expressions may not convey to him any very distinct meaning, their import is perfectly understood by philosophers. It is now, I think pretty generally acknowledged by physiologists, that the influence of the will over the body, is a mystery which has never yet been unfolded; but singular as it may appear, Dr. Reid was the first person who had courage to lay completely aside all the common hypothetical language concerning perception, and to exhibit the difficulty in all its magnitude, by a plain statement of the fact. To what then, it may be asked, does this statement amount ?-Merely to this; that the mind is so formed, that certain impressions produced on our organs of sense by external objects are followed by correspondent sensations; and that these sensations, (which have no more resemblance to the qualities of matter, than the words of a language have to the things they denote,) are followed by a perception of the existence and qualities of the bodies by which the impressions are made; that all the steps of this process are equally incomprehensible; and that, for any thing we can prove to the contrary, the connexion between the sensation and the perception, as well as that between the impression and the sensation, may be both arbitrary; that it is therefore by no means impossible, that our sensations may be merely the occasions on which the correspondent perceptinos are excited; and that, at any rate, the consideration of these sensations, which are attributes of mind can throw no light on the manner in which we acquire our knowledge of the existence and qualities of body. From this view

of the subject, it follows, that it is external objects themselves, and not any species or images of these objects, that the mind perceives; and that although, by the constitution of our nature, certain sensations are rendered the constant antecedents of our perceptions, it is just as difficult to explain how our perceptions are obtained by their means, as it would be, upon the supposition, that the mind were all at once inspired with them, without any concomitant sensations whatever.

These remarks are general, and apply to all our various perceptions; and they evidently strike at the root of all the common theories upon the subject. The laws, however, which regulate these perceptions, are different in the case of the different senses, and form a very curious object of philosophical inquiry.-Those, in particular, which regulate the acquired perceptions of sight, lead to some very interesting and important speculations; and, I think, have never yet been explained in a manner completely satisfactory. To treat of them in detail, does not fall under the plan of this work; but I shall have occasion to make a few remarks on them, in the chapter on Conception.

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In opposition to what I have here observed on the importance of Dr. Reid's speculations concerning our perceptive powers, I am sensible it may be urged, that they amount merely to a negative discovery; and it is possible, that some may even be forward to remark, that it was necessary to employ so much labour and ingenuity as he has done to overthrow an hypothesis of which a plain account would have been a sufficient refutation. To such persons I would beg leave to suggest that although, in consequence of the juster views in pneumatology, which now begin to prevail, (chiefly, I believe in consequence of Dr. Reid's writings,) the ideal system may appear to many readers unphilosophical and puerile: yet the case was very different when this author entered upon his inquiries: and I may even venture to add, that few positive discoveries, in the whole history of science, can be mentioned, which found a juster claim to literary reputation, than to have detected, so clearly and unanswerably, the fallacy of an hypothesis, which has descended to us from the earliest ages of philosophy; and which, in modern times, has not only served to Berkeley and Hume as the basis of their sceptical systems, but was adopted as an indisputable truth by Locke, by Clarke, and by Newton.

SECTION IV.

Of the Origin of our Knowledge.

THE philosophers who endeavour to explain the operations of the human mind by the theory of ideas, and who took for granted, that in every exertion of thought there exists in the mind some object distinct from the thinking substance, were naturally led to inquire whence these ideas derive their origin; in particular, whether they are conveyed to the mind from without by means of the senses, or form part of its original furniture ?

With respect to this question, the opinions of the ancients were varibut as the influence of these opinions on the prevailing systems of for any the present age is not very considerable, it is not necessary,

ous;

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