"Plato has profoundly defined man 'the hunter of truth;' for in this chase, as in others, the pursuit is all in all, the success comparatively nothing. We exist only as we energize; pleasure is the reflex of unimpaired energy; energy is the mean by which our faculties are developed; and a higher energy, the end which their development proposes. In action is thus contained the existence, happiness, improvement, and perfection of our being; and knowledge is only precious, as it may afford a stimulus to the exercise of our powers, and the condition of their more complete activity. Speculative truth is, therefore, subordinate to speculation itself; and its value is directly measured by the quantity of energy which it occasions, — immediately in its discovery, mediately through its consequences. Life to Endymion was not preferable to death; aloof from practice, a waking error is better than a sleeping truth. Neither, in point of fact, is there found any proportion between the possession of truths, and the development of the mind in which they are deposited. Every learner in science is now familiar with more truths than Aristotle or Plato ever dreamt of knowing; yet, compared with the Stagirite or the Athenian, how few, even of our masters of modern science, rank higher than intellectual barbarians.” - Ib. p. 40.

"All profitable study is a silent disputation an intellectual gymnastic; and the most improving books are precisely those which most excite the reader to understand the author, to supply what he has omitted, and to canvass his facts and reasonings. To read passively, to learnis, in reality, not to learn at all. In study, implicit faith, belief upon authority, is worse even than, for a time, erroneous speculation. To read profitably, we should read the authors, not most in unison with, but most adverse to, our opinions; for whatever may be the case in the cure of bodies, enantiopathy, and not homopathy, is the true medicine of minds. Accordingly, such sciences and such authors, as present only unquestionable truths, [pure mathematics, for instance, when made a chief object of pursuit,] determining a minimum of self-activity in the student, are, in a rational education, subjectively, naught. Those [such] sciences and authors, on the contrary, as constrain the student to independent thought, [metaphysics, for example,] are, whatever be their objective certainty, subjectively, educationally, best."]—Ib. p. 773.

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PHILOSOPHY

OF

THE HUMAN MIND.

CHAPTER I.

OF THE POWERS OF EXTERNAL PERCEPTION.

I. Of the theories which have been formed by Philosophers, to explain the manner in which the MIND perceives external Objects.— Among the various phenomena which the human mind presents to our view, there is none more calculated to excite our curiosity and our wonder, than the communication which is carried on between the sentient, thinking, and active principle within us, and the material objects with which we are surrounded. How little soever the bulk of mankind may be disposed to attend to such inquiries, there is scarcely a person to be found, who has not occasionally turned his thoughts to that mysterious influence, I which the will possesses over the members of the body; and to those powers of perception which seems to inform us, by a sort of inspiration, of the various changes which take place in the external universe. Of those who receive the advantages of a liberal education, there are perhaps few, who pass the period of childhood, without feeling their curiosity 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.

Which sense is alone considered in most theories of percep tion. 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 preeminence 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.

Objections to all the hypotheses that have been framed to explain the process of perception. 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 following 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.

The doctrine of mediate perception, or of perception through the intervention of images or ideas. - It was the doctrine of Aristotle, (says Dr. Reid,) that as our senses cannot receive external material objects themselves, they receive their species; that is, their images or forms, without the matter; as wax receives the form of the seal, without any of the matter of it. These 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 last, of pure intellection. When they are objects of memory and of imagination, they get the name of phantasms. When, by further refinement, and being stripped of their peculiarities, 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 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.

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

"Plato's subterranean cave, and Mr. Locke's dark closet, may be applied with ease to all the systems of perceptions that have been invented: for they all suppose, 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; 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."

Objections to this doctrine of mediate perception. The very short and imperfect view we have now taken of the common theories of perception, is almost 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, (1.) 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, (2.) of the essential distinction between mind and matter; which, although not ren