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Different instruments, such as a flute, a violin, and a bass-viol, may all sound the same tone, and yet be easily distinguishable. A considerable number of human voices may sound the same note, and with equal strength, and yet there will be some difference. The same voice, while it maintains the proper distinctions of sound, may yet be varied many ways by sickness or health, youth or age, and other alterations in our bodily condition to which we are incident.
Ø 25. Manner in which we learn the place of sounds. It is a fact particularly worthy of notice in respect to sounds, that we should not know, previous to all experience on the subject, whether a sound came from the right or left, from above or below, from a smaller or greater distance. And this will appear the less surprising when we remember that the undulations of air are always changed from their original direction by the channels and the windings of the ear before they strike the tympanum. Abundant facts confirm this statement.
Dr. Reid mentions, that once, as he was lying in bed, having been put into a fright, he heard his own heart beat. He took it to be some one knocking at the door, and arose and opened the door oftener than once before he discovered that the sound was in his own breast. Some traveller has related that, when he first heard the roaring of a lion in a desert wilderness, not seeing the animal, he did not know on what side to apprehend danger, as the sound seemed to him to proceed from the ground, and to enclose a circle, of which he and his companions stood in the centre.
It is by custom or experience that we learn to distinguish the place of things, and, in some measure also, their nature, by means of their sound. It is thus that we learn that one noise is in a contiguous room, that another is above our heads, and another is in the street. And what seems to be an evidence of this is, that when we are in a strange place, after all our experience, we very frequently find ourselves mistaken in these respects,
If a man born deaf were suddenly made to hear, he would probably consider his first sensations of sound as
originating wholly within himself
. But in process of time we learn not only to refer the origin of sounds to a position above or below, to the right or left; but to connect each particular sound with a particular external cause, referring one to a bell as its appropriate external cause, another to a flute, another to a trumpet.
THE SENSE OF TOUCH.
$ 26. Of the sense of touch in general and its sensations. We are next to consider the sense of TOUCH. The principal organ of this sense is the hand, although it is not limited to that part of our frame, but is diffused over the whole body. The hand principally arrests our attention as the organ of this sense, because, being furnished with various articulations, it is easily moveable by the muscles, and can readily adapt itself to the various changes of form in the objects to which it is applied.
The senses, which have hitherto been examined, are more simple and uniform in their results than that of the touch. By the ear we merely possess that sensation which we denominate hearing; we have the knowledge of sounds, and that is all. By the palate we acquire a knowledge of tastes, and by the sense of smelling we become acquainted with the odours of bodies. The knowledge which is directly acquired by all these senses is limited to the qualities which have been mentioned. By the sense of touch, on the contrary, we become acquainted not with one merely, but with a variety of qualities, such as the following, heat and cold, hardness and softness, roughness and smoothness, solidity or resistance, extension, and figure; and, in particular, it gives occasion for the origin of the antecedent and more general notion of externality
$ 27. Idea of externality suggested in connexion with the touch.
If man were possessed of the sense of smell alone, it would be found that the earliest elements of his knowl
edge consisted exclusively in sensations of odours. According, however, as these sensations were agreeable or disagreeable, he would acquire the additional ideas of pleasure and pain. And having experienced pleasure and pain, we may suppose that this would subsequently give rise both to the feelings and the abstract conceptions of desire and aversion. But if he had no other sense, all these feelings would seem to him to be internal, not only in their experience, but their origin; in other words, to be mere emanations from the soul itself; and he would be incapable of referring them to an external cause. If he were possessed of the sense of hearing alone, the result would be similar; his existence would then seem to consist essentially of sounds, as in the other case it would be made up of odours; nor, indeed, by the aid of merely both these senses combined would he be able to form an idea of externality or outwardness.
But this idea is a most important one; it is the connecting thought which introduces us to an acquaintance with a new form of existence, different from that interior existence which we variously call by the names spirit, mind, or soul. This idea first arises in the mind, although it is not directly addressed to that sense, by means of the touch.
There is no question that the other senses might of themselves furnish a basis of considerable extent for the mental action. By means of their aid alone, such a de
, perceive, think, compare, abstract, reason, and will. And although, under such circumstances, everything would seem to us to be internal, yet we should probably find * the mental action unembarrassed and easy, and a source
of pleasure. But after a time we decide to move the limbs in a particular direction, and to press the hand or some other part of the body through some hard and resisting substance. It is when we attempt to do anything of this kind, which calls the sense of touch into action, that we find the wonted series of thoughts disturbed, the desire checked, and the volition counteracted. It is probably at this precise position of the mind, with scarcely the interval of a momentary pause of wonder, that
there arises vividly in the soul a new perception, a new thought, which we call the idea of externality or outness. It is the sense of touch which impinges upon the obstacle that stands in our way; and no other sense admits of this peculiar application. It is thus the means of partially disturbing the previous connexion and tendency of thought, and of giving occasion for the rise of the new idea which is under consideration. And this idea, called into existence under these circumstances, becomes associated with all those notions which we subsequently form of matter.-It may be of some importance to add here, that we shall have occasion to refer to this idea again under the head of Original Suggestion. It is to be remembered, that externality is not a direct object of the touch, as extension and hardness are, but that the tactual
imply furnishes the occasion on which it is formed. Ø 28. Origin of the notion of extension, and of form or figure. The idea of EXTENSION has its origin by means of the sense of touch. When the touch is applied to bodies, where in the intermediate parts there is a continuity of the same substance, we necessarily form that notion. It is not, however, to be imagined that Extension, as it exists outwardly, and the corresponding notion in the mind, actually resemble each other. So far from any imitation and copying from one to the other, or resemblance in any way, there is a radical and utter diversity. As to outward, material extension, it is not necessary to attend to it here; our business at present is with the corresponding inward feeling. Nor will it be necessary to delay even upon that; the more we multiply words upon it, the more obscure it becomes. As it is a simple idea, we cannot resolve it into others, and in that way make it clearer by defining it. We must refer in this case, as in others like it, to each one's personal experience. It will be better understood in that way than by any form of words.
The notion of extension is intimately connected with, and may be considered in some sort the foundation of, that of the FORM or figure of bodies.—Dr. Brown somewhere calls the Form of bodies their relation to each other in space. This is thought to afford matter for reflection;
but when we consider that SPACE, whatever it may be objectively or outwardly, exists in the mind as a simple notion, and that the particular relation here spoken of is not pointed out, the remark may not be found to throw much light on the subject. Still we do not suppose that any one is ignorant of what FORM is; men must be supposed to know that, if they are thought to know anything. All that is meant to be asserted here is, that the idea of extension is antecedent, in the order of nature, to that of form; and that the latter could not exist without the other; but that both, nevertheless, are simple, and both are to be ascribed to the sense of touch.
$ 29. On the sensations of heat and cold. Among the states of mind which are usually classed with the intimations of the sense under consideration, are those which are connected with changes in the temperature of our bodies. Some writers, it is true, have been inclined to dissent from this arrangement, and have hazarded an opinion that they ought not to be ascribed to the sense of Touch; but Dr. Reid, on the contrary, who gave to our sensations the most careful and patient attention, has decidedly assigned to them this origin. Among other remarks, he has expressed himself on this subject to this effect.
“The words heat and cold,” he remarks, (Inquiry into the Human Mind, ch. v.,)“ have each of them two significations; they sometimes signify certain sensations of the mind, which can have no existence when they are not felt, nor can exist anywhere but in the mind or sentient being; but more frequently they signify a quality in bodies, which, by the laws of nature, occasions the sensations of heat and cold in us; a quality which, though connected by custom so closely with the sensation that we cannot without difficulty separate them, yet hath not the least resemblance to it, and may continue to exist when there is no sensation at all.
“The sensations of heat and cold are perfectly known, for they neither are, nor can be, anything else than what we feel them to be; but the qualities in bodies, which we call heat and cold, are unknown. They are only conceiv