The sensations of _heat_ and _cold_,--as received from our organ of touch,--we may almost lay out of account in our analytical inquiry. It is unnecessary to dwell on them, or even to repeat, in application to them, the argument, which has been already applied more than once to the sensations before considered. It is quite evident, that, in classing our warmth or chillness, as a sensation,--and not as a feeling that has arisen spontaneously in the mind,--we are influenced by that experience, which has previously given us the belief of objects external,--at least, of our own corporeal frame,--and that, if we had been unsusceptible of any other sensations, than those of heat and cold, we should as little have believed these to arise directly from a corporeal cause, as any of our feelings of joy or sorrow. The same remark may be applied to the painful sensations of puncture and laceration. It is only to the other more important information ascribed to the sense of touch, therefore, that our attention is to be directed. By _touch_, we are commonly said to be made acquainted with extension, magnitude, divisibility, figure, motion, solidity, liquidity, viscidity, hardness, softness, roughness, smoothness. These terms, I readily allow, are very convenient for expressing notions of certain forms or states of bodies, that are easily distinguishable. But, though specifically distinguishable, they admit generically of very considerable reduction and simplification. Hardness and softness, for example, are expressive only of greater or less resistance,--roughness is irregularity of resistance, when there are intervals between the points that resist, or when some of these points project beyond others,--smoothness is complete uniformity of resistance,--liquidity, viscidity, are expressive of certain degrees of yieldingness to our effort, which solidity excludes, unless when the effort employed is violent. All, in short, I repeat, are only different species or degrees of that which we term _resistance_, whatever it may be, which impedes our continued effort, and impedes it variously as the substances without are themselves various. Such is one order, then, of the feelings commonly ascribed to the sense which we are at present considering.