ELEMENTS

OF THE

PHILOSOPHY OF THE HUMAN MIND.

CHAPTER FIRST.

OF THE POWERS OF EXTERNAL PERCEPTION.

SECTION 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, which the will possesses over the members of the body, and to those powers of perception, which seem 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.

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 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 deeprooted, 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 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. 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 last, of "pure intellection. When they are objects of memory and of imagina"tion, they get the name of phantasms. When, by farther refinement, "and being stripped 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."

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"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 แ 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 external 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 dif ference 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.†

"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 perception, 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 common"ly been called ideas ; and by Mr. Hume, impressions. But all philo"sophers, from Plato to Mr. Hume, agree in this, that we do not per"ceive 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 (C a nature."||

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The very short and imperfect review 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, 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 † Ibid. p. 99.

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

+ Locke on Human Understanding, book ii. chap. 11. § 17.

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 contradictory." As to objects of sight," says Dr. Reid, "I understand what is "meant by an image of their figure in the brain: but how shall we con❝ceive an image of their colour, where there is absolute darkness? And, as to all other objects of sense, except figure and colour, I am unable "to conceive what is meant by an image of them. Let any man say, "what he means by an image of heat and cold, an image of hardness ❝or softness, an image of sound, or smell, or taste. The word image, "when applied to these objects of sense, has absolutely no meaning " This palpable imperfection in the ideal theory, has plainly taken rise from the natural order in which the phenomena of perception present themselves to the curiosity.

The mistakes, which have been so long current in the world, about this part of the human constitution, will, I hope, justify me for prosecuting the subject a little farther; in particular, for illustrating, at some length, the first of the two general remarks already referred to. This speculation I enter upon the more willingly, that it affords me an opportunity of stating some important principles with respect to the object and the limits of philosophical inquiry, to which I shall frequently have occasion to refer in the course of the following disquisitions.

SECTION II.

Of certain natural Prejudices, which seem to have given rise to the common Theories of Perception.

It seems now to be pretty generally agreed among philosophers, that there is no instance in which we are able to perceive a necessary connexion between two successive events, or to comprehend in what manner the one proceeds from the other, as its cause. From experience,

VOL. I.

6

indeed, we learn, that there are many events, which are constantly conjoined, so that the one invariably follows the other: but it is possible, for any thing we know to the contrary, that this connexion, though a constant one, as far as our observation has reached, may not be a necessary connexion nay, it is possible, that there may be no necessary connexions among any of the phenomena we see; and if there are any such connexions existing, we may rest assured that we shall never be able to discover them.*

I shall endeavour to shew, in another part of this work, that the doctrine I have now stated does not lead to those sceptical conclusions, concerning the existence of a First Cause, which an author of great ingenuity has attempted to deduce from it.-At present, it is sufficient for my purpose to remark, that the word cause is used, both by philosophers and the vulgar, in two senses, which are widely different.When it is said, that every change in nature indicates the operation of a cause the word cause expresses something which is supposed to be necessarily connected with the change, and without which it could not have happened. This may be called the metaph, sical meaning of the word; and such causes may be called metaphysical or efficient causes.-In natural philosophy, however, when we speak of one thing being the cause of another, all that we mean is, that the two are constantly conjoined, so that, when we see the one, we may expect the other. These conjunctions we learn from experience alone, and, without an acquaintance with them, we could not accommodate our conduct to the established course of nature.-The causes which are the objects of our investigation in natural philosophy, may, for the sake of distinction, be called physical

causes.

I am very ready to acknowledge, that this doctrine, concerning the object of natural philosophy, is not altogether agreeable to popular prejudices. When a man, unaccustomed to metaphysical speculations, is told, for the first time, that the science of physics gives us no information concerning the efficient causes of the phenomena about which it is employed, he feels some degree of surprise and mortification. The natural bias of the mind is surely to conceive physical events as somehow linked together, and material substances as possessed of certain powers and virtues, which fit them to produce particular effects. That we have no reason to believe this to be the case, has been shewn in a very satisfactory manner by Mr. Hume, and by other writers, and must, indeed, appear evident to every person, on a moments reflection. It is a curious question, what gives rise to the prejudice?

In stating the argument for the existence of the Deity, several modern philosophers have been at pains to illustrate that law of our nature, which leads us to refer every change we perceive in the universe, to the operation of an efficient cause.t-This reference is not the result of reasoning, but necessarily accompanies the perception, so as to render it impossible for us to see the change, without feeling a conviction of the operation of some cause by which it was produced; much in the same manner, in which we find it to be impossible to conceive a sensation, without being impressed with a belief of the existence of a sentient

See Note (C.)

† See in particular, D. Reid's Essays on the Intellectual Powers of Man.