All they do is to constitute the latent ground-work which the other supervening circumstances have to work upon and whatever influence those original principles may have, is so changed and modified, and covered over, as it were, by those other circumstances, as never to be separately discernible. The effects of the one influence are indistinguishably blended with those of the other. The emotions of the body are received, and with reason, as probable indications of the temperature of the mind. But they are far enough from conclusive. A man may exhibit, for instance, the exterior appearances of grief, without really grieving at all, or at least in any thing near the proportion in which he appears to grieve.
Many men can command the external appearances of sensibility with very little real feeling.
To have this kind of command over one's self, was the characteristic excellence of the orator of ancient times, and is still that of the player in our own. The remaining circumstances may, with reference to those already mentioned, be termed secondary influencing circumstances. These have an influence, it is true, on the quantum or bias of a man's sensibility, but it is only by means of the other primary ones. The manner in which these two sets of circumstances are concerned, is such that the primary ones do the business, while the secondary ones lie most open to observation. Among such of the primitive modifications of the corporeal frame as may appear to influence the quantum and bias of sensibility, the most obvious and conspicuous are those which constitute the sex.