excited by this incomprehensible communication between mind and matter. For my own part, at least, I cannot recollect the date of my earliest speculations on the subject.

It is to the phenomena of perception alone, that I am to confine myself in the following essay; and even with respect to these, all that I propose, is to offer a few general remarks on such of the common mistakes concerning them, as may be most likely to mislead us in our future inquiries. Such of my readers as wish to consider them more in detail, will find ample satisfaction in the writings of Dr. Reid.

In considering the phenomena of perception, it is natural to suppose, that the attention of philosophers would be directed, in the first instance, to the sense of seeing. The variety of information and of enjoyment we receive by it, the rapidity with which this information and enjoyment are conveyed to us, and above all, the intercourse it enables us to maintain with the more distant part of the universe, cannot fail to give it, even in the apprehension of the most careless observer, a pre-eminence over all our other perceptive faculties. Hence it is, that the various theories, which have been formed to explain the operations of our senses, have a more immediate reference to that of seeing; and that the greater part of the metaphysical language, concerning perception in general, appears evidently, from its etymology, to have been suggested by the phenomena of vision. Even when applied to this sense, indeed, it can at most amuse the fancy, without conveying any precise knowledge; but, when applied to the other senses, it is altogether absurd and unintelligible.

It would be tedious and useless, to consider particularly the different hypotheses, which have been advanced upon this subject. To all of them, I apprehend, the two fol

lowing remarks will be found applicable: First, that, in the formation of them, their authors have been influenced by some general maxims of philosophizing, borrowed from physics; and, secondly, that they have been influenced by an indistinct, but deep-rooted, conviction of the immateriality of the soul; which, although not precise enough to point out to them the absurdity of attempting to illustrate its operations by the analogy of matter, was yet sufficiently strong, to induce them to keep the absurdity of their theories as far as possible out of view, by allusions to those physical facts, in which the distinctive properties of matter are the least grossly and palpably exposed to our observation. To the former of these circumstances is to be ascribed the general principle, upon which all the known theories of perception proceed; that, in order to explain the intercourse between the mind and distant objects, it is necessary to suppose the existence of something intermediate, by which its perceptions are produced; to the latter, the various metaphorical expressions of ideas, species, forms, shadows, phantasms, images; which, while they amused the fancy with some remote analogies to the objects of our senses, did not directly revolt our reason, by presenting to us any of the tangible qualities of body.

"It was the doctrine of Aristotle, (says Dr. Reid) "that, as our senses cannot receive external material ob"jects themselves, they receive their species; that is, "their images or forms, without the matter; as wax re"ceives the form of the seal, without any of the matter of "it. The images or forms, impressed upon the senses, "are called sensible species; and are the objects only of "the sensitive part of the mind: but by various, internal powers, they are retained, refined, and spiritualized, so "as to become objects of memory and imagination; and, at

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"last, of pure intellection. When they are objects of "memory and of imagination, they get the name of phan"tasms. When, by farther refinement, and being strip

ped of their particularities, they become objects of "science, they are called intelligible species; so that "every immediate object, whether of sense, of memory, "of imagination, or of reasoning, must be some phantasm, "or species, in the mind itself.

"The followers of Aristotle, especially the schoolmen, "made great additions to this theory; which the author "himself mentions very briefly, and with an appearance "of reserve. They entered into large disquisitions with "regard to the sensible species, what kind of things they "are; how they are sent forth by the object, and enter "by the organs of the senses; how they are preserved, "and refined by various agents, called internal senses, "concerning the number and offices of which they had "many controversies."*

The Platonists, too, although they denied the great doctrine of the Peripatetics, that all the objects of human understanding enter at first by the senses, and maintained, that there exist eternal and immutable ideas, which were prior to the objects of sense, and about which all science was employed; yet appear to have agreed with them in their notions concerning the mode in which external objects are perceived. This Dr. Reid infers, partly from the silence of Aristotle about any difference between himself and his master upon this point, and partly from a passage in the seventh book of Plato's Republic; in which he compares the process of the mind in perception, to that of a person in a cave, who sees not external objects themselves, but only their shadows.t

* Essays on the Intellectual Powers of Man, p. 25.

+ Ibid. p. 99.

"Two thousand years after Plato, (continues Dr. Reid,) "Mr. Locke, who studied the operations of the human "mind so much, and with so great success, represents our "manner of perceiving external objects, by a similitude very much resembling that of the cave." Methinks," says he, "the understanding is not much unlike a closet, wholly shut from light, with only some little opening left, "to let in external visible resemblances or ideas of things "without. Would the pictures coming into such a dark room but stay there, and lie so orderly as to be found

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upon occasion, it would very much resemble the under"standing of a man, in reference to all objects of sight, "and the ideas of them."*

"Plato's subterranean cave, and Mr. Locke's dark clo"set, may be applied with ease to all the systems of "perception, that have been invented: for they all sup

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pose that we perceive not external objects immediately, "and that the immediate objects of perception are only "certain shadows of the external objects. Those shadows, "or images, which we immediately perceive, were by the "ancients called species, forms, phantasms. Since the "time of Des Cartes, they have commonly been called "ideas ;t and by Mr. Hume, impressions. But all "philosophers, from Plato to Mr. Hume, agree in this, "that we do not perceive external objects immediately; "and that the immediate object of perception must be "some image present to the mind." On the whole, Dr. Reid remarks, "that in their sentiments concerning perception there appears an uniformity, which rarely occurs upon subjects of so abstruse a nature."‡

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The very short and imperfect review we have now taken of the common theories of perception, is almost

Locke on Human Understanding, book ii. chap. 11. § 17. +See Note (B.)

Reid, p. 116, 117.,

sufficient, without any commentary, to establish the truth of the two general observations formerly made; for they all evidently proceed on a supposition, suggested by the phenomena of physics, that there must of necessity exist some medium of communication between the objects of perception and the percipient mind, and they all indicate a secret conviction in their authors, of the essential distinction between mind and matter; which, although not rendered, by reflection, sufficiently precise and satisfactory, to shew them the absurdity of attempting to explain the mode of their communication, had yet such a degree of influence on their speculations, as to induce them to exhibit their supposed medium under as mysterious and ambiguous a form as possible, in order that it might remain doubtful, to which of the two predicaments, of body or mind, they meant that it should be referred. By refining away the grosser qualities of matter; and by allusions to some of the most aerial and magical appearances it assumes, they endeavoured, as it were, to spiritualize the nature of their medium; while, at the same time, all their language concerning it, implied such a reference to matter, as was necessary for furnishing a plausible foundation, for applying to it the received maxims of natural philosophy.

Another observation, too, which was formerly hinted at, is confirmed by the same historical review; that, in the order of inquiry, the phenomena of vision had first engaged the attention of philosophers, and had suggested to them the greater part of their language with respect to perception in general; and that, in consequence of this circumstance, the common modes of expression on the subject, unphilosophical and fanciful at best, even when applied to the sense of seeing, are, in the case of all the other senses, obviously unintelligible and self-contradic