Lectures on the Philosophy of the Human Mind (Vol. 1 of 3)

by Thomas Brown

In defining sensation, when we began our inquiry into its nature, I stated it to be that affection of the mind, which is immediately subsequent to the affection of certain organs, induced by the action of external bodies; and I admitted, that, in this definition two assumptions were made,—the existence of foreign changeable external bodies, as separate from the mind,—and the existence of organs, also separate from the mind, and in relation to it truly external, like other bodies, but forming a permanent part of our corporeal frame, and capable of being affected, in a certain manner, by the other bodies, of which the existence was assumed. As far as our analytical inquiry has yet proceeded, these assumptions are assumptions still. We have not been able to detect, in the sensations considered by us, more than in any of our internal pleasures or pains, any circumstances that seem to be indicative of a material world without.

Our analytical inquiry itself, however, even in attempting to trace the circumstances, in which the belief originates, must proceed on that very belief. Accordingly, in examining our senses of smell, taste, and hearing, I uniformly took for granted the existence of odoriferous, sapid, and vibrating bodies, and considered merely, whether the sensations, excited by these, were, of themselves, capable of communicating to us any knowledge of the external and independent existence of the bodies which excited them.

In the present stage of our inquiry, I must, in like manner, take for granted the existence of bodies, which act, by their contiguity or pressure, on our organ of touch, as the odoriferous or sapid particles, act on our nerves of smell and taste—not that I assume this belief, as existing in the mind whose intellectual acquisitions are the subject of inquiry,—for, in that case, the inquiry itself would be superfluous. I assume it, merely as existing in the mind of us the inquirers,—and only, because it is impossible, without such an assumption to make the suppositions that are necessary for the inquiry. All our language is at present adapted to a system of external things. There is no direct vocabulary of scepticism; and even the most cautious and philosophic inquirer, therefore, must often be obliged to express his doubt, or his dissent, in language that implies affirmation. In the present case, when we attempt to analyse our sensations, it is impossible to speak of the circumstances in which the infant is placed, or, I may say even, to speak of the infant himself, without that assumption which we have been obliged to make. The real existence of an external universe, and the belief of that existence, are, however, in themselves, perfectly separate and distinct; and it is not the existence of an external world, which we are now endeavouring to establish as an object of belief. We are only endeavouring, in our analysis of the sensations afforded by our different organs, to ascertain in what circumstance the belief arises. There might be a world of suns and planets, though there were no human being, whose mind could be affected with belief of it; and even the most zealous defenders of the reality of external nature must admit, that, though no created thing but ourselves were in existence, our mind might still have been so constituted, as to have the very series of feelings, which form at present its successive phenomena, and which are ascribed in no small number to the action of external things.

Are the primary sensations derived from the organ of touch, then, of such a kind as to afford us that knowledge, which they are supposed to give of things without?

Let us imagine a being, endowed with the sense of touch, and with every other sense and faculty of our mind, but not with any previous knowledge of his own corporeal frame, or of other things external,—and let us suppose a small body, of any shape, to be pressed, for the first time, on his open hand. Whatever feelings mere touch can give, directly of itself, would of course be the same in this case, as now, when our knowledge is increased, and complicated, from many other sources.

Let the body, thus impressed, be supposed to be a small cube, of the same temperature with the hand itself, that all consideration of heat or cold may be excluded, and the feeling produced be as simple as possible.

What, then, may we suppose the consequent feeling to be?

It will, I conceive, be a simple feeling of the kind of which I have already spoken, as capable of arising from the affection of a single point of our organ of touch,—a feeling that varies indeed with the quantity of pressure, as the sensation of fragrance varies with the number of the odorous particles, but involves as little the notion of extension, as that notion is involved in the mere fragrance of a violet or a rose. The connection of this original tactual feeling, however, with that of extension, is, now, so indissoluble, as, indeed, it could not fail to become, in the circumstance in which it has uniformly arisen, that it is almost impossible to conceive it as separate. We may perhaps, however, make a near approach to the conception of it, by using the gentle gradual pressure of a small pointed body, which, in the various slight feelings, excited by it,—before it penetrate the cuticle, or cause any considerable pain,—may represent, in some measure, the simple and immediate effect, which pressure in any case produces,—exclusively of the associate feelings which it indirectly suggests.

Such of you, as have the curiosity to try the experiment, with any small bodies, not absolutely pointed,—such as the head of a pin, or any body of similar dimensions,—will be astonished to feel, how very slightly, if at all, the notion of extension or figure is involved in the feeling, even after all the intimate associations of our experience;—certainly far less than the notion of longitudinal distance seems to us to be involved in the immediate affections of our sense of sight. It is an experiment, therefore, which I must request you not to neglect to make.

But the pressure of such a large body, as the cube, which we have supposed to be pressed against our organ of touch, now awakens very different feelings. We perceive, as it were immediately, form and hardness. May not, then, the knowledge of resistance and extension, and consequently the belief of the essential qualities of matter,—be originally communicated by the affections of this organ?