ly 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 or attributes, such as the following, heat and cold, hardness and softness, roughness and smoothness, resistance, extension, and figure; and in particular, it is in the applications of this sense, that we find an occasion furnished for the origin of the antecedent and more general notion of externality.

§. 70. Idea of externality suggested in connection with the touch.

If man were possessed of the sense of smell alone, it would be found, that the earliest elements of his knowledge consisted exclusively in sensations of odors. 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 odors; nor indeed by the aid of merely both these senses combined, would he be able to form an idea of externality or outness.

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 developement of the mind might take place, that we could perceive, think, compare, abstract, reason, and will. And, although under

such circumstances, every thing 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 any thing 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 connection 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 sense simply furnishes the occasion, on which it is formed.

§. 71. 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 any thing. 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.

§. 72. 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, Chap. 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 any where 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 qualily, 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, any thing else than what we feel them to be; but the qualities in bodies, which we call heat and cold are unknown. They are only conceived by us, as unknown causes or occasions of the sensations, to which we give the same names. But though common sense says nothing of the nature of the qualities, it plainly dictates the existence of them; and to deny that there can be heat and cold when they are not felt, is an absurdity too gross to merit confutation. For what could be more absurd, than to say, that the thermometer cannot rise or fall, unless some person be present, or that the coast of Guinea would be as cold as Nova Zembla, if it had no inhabitants.

"It is the business of philosophers to investigate by proper experiments and induction, what heat and cold are in bodies. And whether they make heat a particular element diffused through nature, and accumulated in the heated body, or whether they make it a certain vibration of the parts of the heated body; whether they determine that heat and cold are contrary qualities, as the sensations undoubtedly are contrary, or that heat only is a quality, and cold its privation; these questions are within the province of philosophy; for common sense says nothing on the one side or the other.

"But whatever be the nature of that quality in bodies which we call heat, we certainly know this, that it cannot in the least resemble the sensation of heat. It is no less absurd to suppose a likeness between the sensation and the quality, than it would be to suppose, that the pain of the gout resem bles a square or a triangle. The simplest man, that hath common sense, does not imagine the sensation of heat, or any thing that resembles that sensation, to be in the fire. He on ly imagines, that there is something in the fire, which makes him and other sentient beings feel heat. Yet as the name of heat, in common language, more frequently and more proper ly signifies this unknown something in the fire, than the sen sation occasioned by it, he justly laughs at the philosopher

who denies that there is any heat in the fire, and thinks that he speaks contrary to common sense."

§. 73. On the sensation of hardness and softness.

"Let us next consider, (continues the same writer,) HARDNESS AND SOFTNESS; by which words we always understand real properties or qualities of bodies, of which we have a distinct conception.

:

"When the parts of a body adhere so firmly that it cannot easily be made to change its figure, we call it hard; when its parts are easily displaced, we call it soft. This is the notion which all mankind have of hardness and softness they are neither sensations, nor like any sensation; they were real qualities before they were perceived by touch, and continue to be so when they are not perceived: for if any man will affirm that diamonds were not hard till they were handled, who would reason with him?

"There is, no doubt, a sensation by which we perceive a body to be hard or soft. This sensation of hardness may easily be had, by pressing one's hand against a table, and attending to the feeling that ensues, setting aside, as much as possible, all thought of the table and its qualities, or of any external thing. But it is one thing to have the sensation, and another to attend to it and make it a distinct object of reflection. The first is very easy; the last, in most cases, extremely difficult.

"We are so accustomed to use the sensation as a sign, and to pass immediately to the hardness signified, that, as far as appears, it was never made an object of thought, either by the vulgar, or by philosophers; nor has it a name in any language. There is no sensation more distinct, or more frequent; yet it is never attended to, but passes through the mind instantaneously, and serves only to introduce that quality in bodies, which, by a law of our constitution, it suggests.

There are indeed some cases, wherein it is no difficult matter to attend to the sensation occasioned by the hardness of a body; for instance, when it is so violent as to occasion considerable pain: then nature calls upon us to attend to it; and then we acknowledge that it is a mere sensation, and can