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 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 mentai state. 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 state, 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 found

ation of, that of the FORM or figure of bodies.-Dr. Brown somewhere calls the Form of bodies their relation to each other in space. And it is very true that the form of bodies involves the fact of the relation of their parts to each other. But we do not propose here to consider form in its outward existence, but only the idea or mental state which corresponds to it. The notion which we have of the form of things is subsequent, in the order of nature, to that which we have of their extension. The former could not exist without the antecedent existence of the latter. Both are simple; both are undefinable; 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 haz arded 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 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 con ceived 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 resembles a square or a triangle. The simplest man that hath common sense does not imagine the sensation of heat, or anything that resembles that sensation, to be in the fire. He only 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 properly signifies this unknown something in the fire than the sensation 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." 12

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73. On the sensations 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 until 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 thoughts 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 only be in a sentient being. If a man runs his head with violence against a pillar, I appeal to him whether the pain he feels resembles the hardness

of the stone; or if he can conceive anything like what he feels to be in an inanimate piece of matter.

The attention of the mind is here entirely turned towards the painful feeling; and, to speak in the common language of mankind, he feels nothing in the stone, but feels a violent pain in his head. It is quite otherwise when he leans his head gently against the pillar; for then he will tell you that he feels nothing in his head, but feels hardness in the stone. Hath he not a sensation in this case as well as in the other? Undoubtedly he hath; but it is a sensation which nature intended only as a sign of something in the stone; and, accordingly, he instantly fixes his attention upon the thing signified; and cannot, without great difficulty, attend so much to the sensation as to be persuaded that there is any such thing distinct from the hardness it signifies.

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But, however difficult it may be to attend to this fugitive sensation, to stop its rapid progress, and to disjoin it from the external quality of hardness, in whose shadow it is apt immediately to hide itself: this is what a philosopher by pains and practice must attain, otherwise it will be impossible for him to reason justly on this subject, or even to understand what is here advanced. For the last appeal, in subjects of this nature, must be to what a man. feels and perceives in his own mind.”

§ 74. Of certain indefinite feelings sometimes ascribed to the touch.

In connexion with these views on the sensations of touch, it is proper to remark, that certain feelings have been ascribed to that sense which are probably of a character too indefinite to admit of a positive and undoubted classification. Although they clearly have their place in the general arrangement which has been laid down, with the states of mind which we are now considering; that is to say, are rather of an external and material, than of an internal origin; still they do not so evidently admit of an assignment to a particular sense. Those sensations

to which we now refer (if it be proper to use that term in application to them) appear to have their origin in the human system considered as a whole, made up of bones, flesh, muscles, the senses, &c., rather than to be suscepti