have admitted some sort of distinction between the two, have at the same time treated the distinction as if it were no distinction at all. In their hands it has evaporated in mere empty phrases, and none of them, so far as I know, has ever told us distinctly what sensation is as distinguished from thought, or what thought is as distinguished from sensation. I can assure you, however, that the difference between them is most extreme and momentous. It is so extreme as to justify and bear out the doctrine that man is absolutely distinguished from the lower animals by the power of thought, that thinking is, in fact, his differentia—a doctrine frequently proclaimed, although even the philosophers who have proclaimed it most zealously have never themselves been able, so far as I know, to explain distinctly wherein the distinction consists, or to tell us precisely what thought is as distinguished from sensation.
10. This distinction I shall now attempt to explicate, tracing out what seem to me to be the lines, although they are very faint, of the Socratic design. But, as preparatory to my explication of the nature of thought, let me first try to explain what sensation precisely is. The nature of thought will be better understood when contrasted with the nature of sensation. First, then, of sensation. Each sensation, whatever it may be, is that sensation, and not more than that sensation. It is precisely it, and nothing less than it, nothing more than it. For example,
