CHAP. III.

are few; since, strictly speaking, all are senses of PART I. touch; the impressions upon all being made by contact. There is, nevertheless, one mode of Of Touch. irritation belonging exclusively to the surface of particular parts of the body, which has so little analogy with any other sensation, that it may almost be considered as a sense by itself. This is tickling, which produces that unaccountable convulsion called laughter; a sort of involuntary expression of joy or pleasure, which, when long continued, and carried to excess, becomes painful. It is peculiar, I believe, to the human race, and to the monkey species; though some other animals, such as horses, seem sensible of the sensation which produces it. A similar effect is produced by the operation of certain trains of ideas upon the mind; but this is never so violent

as to be painful.

4. This, indeed, is not the only instance of something like an internal sense of touch; by means of which the conceptions of the mind operate upon the organs of the body involuntarily and mechanically. It is observed by Sir Joshua Reynolds that, if a man born blind were to recover his sight, and the most beautiful woman were brought before him, he could not determine whether she was handsome, or not *. The justice of this remark I

* Discourses.

D

CHAP. III,

of

PART I. shall confirm in treating of vision, by reasons either not known to, or which did not occur to, Of Touch. the great artist, when he made it. At present, I shall only add this further remark, by way corollary, that if a man, perfectly possessed both of feeling and sight-conversant with, and sensible to, the charms of women, were even to be in contact with what he conceived to be the most beautiful and lovely of the sex; and at the moment, when he was going to embrace her, he was to discover that the parts which he touched only were feminine or human; and that, in the rest of her form, she was an animal of a different species, or a person of his own sex, the total and instantaneous change of his sentiments from one extreme to another would abundantly convince him that his sexual desires depended as little upon the abstract sense of touch, as upon that of sight.

5. Are these sexual desires, therefore, governed by any innate images or ideas, according to which the external impressions upon the organs of sense affect us one way or another? Certainly not for the doctrine of innate ideas has been so completely confuted and exploded, that no person in his senses can now entertain it; but, nevertheless, there may be internal stimuli, which, though not innate, grow up constitutionally in the body;

and naturally and instinctively dispose the desires PART. I. of all animals to the opposite sex of their own CHAP. II, species. Animal desire or want may exist with- Of Touch. out any idea of its object, if there be a stimulus

to excite it; so that a male, who had arrived at maturity without knowing the existence of a fe- male of his own species, might feel it, as a newborn child feels the want of food, without having any determinate notion of what was proper to gratify it.

6. Beauty of form and colour, which act, in these cases, through the medium of the imagination only, have nothing to do with this mere irritation of the nerves, whether it proceed from internal or external stimuli; for this irritability' extends in some instances to vegetable substances, which have no power of perception; but of which the organic parts are not only irritable, but require the touch of an insect or other extraneous body to render them effective in reproduction.

7. Many sorts of plants seem, in other respects, capable of sensation, as far as this power consists in the mere aptitude of the organs to receive impressions: but it does not appear that the impressions ever go further than the organs, which receive them; and if they do not, it is evident that they can excite neither pleasure nor

CHAP. III.

PART I., pain; nor leave any traces or memorials behind them of any kind. The impressions, therefore, Of Touch. being unperceived, produce only mechanical vibrations in the fibres, of which the sufferer is not conscious, and which, therefore, only differ in their cause or mode from those which impulse or attraction excites in the component parts of metals: for though the impressions upon the external organs of sense are the primary causes of those sensations, which imprint the ideas of them upon the mind; yet the perception of those sensations, and consequently the pleasures and pains arising from them, as well as the ideas which they imprint, are in the brain; from which, if the organ be separated, though it may retain its irritability, and its apparent sensibility, for a considerable time, it will still be utterly incapable of sensation, and in exactly the same predicament as we have supposed the irritable organs of vegetables to be*: on the contrary,

* I am speaking only of animals whose organization is perfect, and analogous to our own. I know that butterflies, wasps, &c. do appear to be sensible of pleasure or pain, and even live and linger for a long time after their heads are off; but then it does not appear that the heads of such animals contain any centre of organization or seat of life analogous to the brain in birds and quadrupeds. Many of the old-blooded amphibious animals also retain life for a long

CHAP. III.

sensations, exactly resembling those produced PART I. by impressions on the external organs, will continue to be felt when the organ is no more; it Of Touch. being common for a person, who has lost a limb, to imagine that he feels a pain in the extremity which has been amputated; that is, really to feel a pain, excited by some internal cause, similar to that which he had before felt in that extremity.

s. For this, as well as for many other reasons, it is evident that neither the sensations, nor the ideas imprinted by them, have any resemblance to the objects, or the qualities of objects, which have produced them; but that the connection between them, howsoever spontaneous and immediate it may seem, is merely habitual, and the result of experience and observation *. Certain sensations constantly accompanying certain ob

time after the head has been separated from the body; but if there be any sense of pain left, I should conceive it to be in the head only.

* See Locke, Berkeley, Hume, Reid, &c. Locke, indeed, with some hesitation excepted what he calls the primary qualities of bodies, such as figure, extension, &c. and admitted that the ideas of these were resemblances of them, (Essay on Human Understanding, Book II. c. viii.) but Berkeley and Hume found no difficulty in confuting him, and proving that these had no more similitude to their archetypes than any others.