Such, then, was my classification of ideas. And it is a classification over which no dispute is likely to arise, seeing that it merely sets in some kind of systematic order a body of observable facts with regard to which writers of every school are nowadays in substantial agreement. Now, if this classification be accepted, it follows that the question before us is thrown back upon the faculty of language. This faculty, therefore, I considered in a series of chapters. First it was pointed out that, in its widest signification, “language” means the faculty of making signs. Next, I adopted Mr. Mivart’s “Categories of Language,” which, when slightly added to, serve to give at once an accurate and exhaustive classification of every bodily or mental act with reference to which the term can possibly be applied. In all there were found to be seven of these categories, of which the first six are admittedly common to animals and mankind. The seventh, however, is alleged by my opponents to be wholly peculiar to the human species. In other words, it is conceded that animals do present what may be termed the germ of the sign-making faculty; but it is denied that they be able, even in the lowest degree, to make signs of an intellectual kind—_i.e._ of a kind which consists in the bestowing of names as marks of ideas. Brutes are admittedly able to make signs to one another—and also to man—with the intentional purpose of conveying such ideas as they possess; but, it is alleged, no brute is able to name these ideas, either by gestures, tones, or words. Now, in order to test this allegation, I began by giving a number of illustrations which were intended to show the level that is reached by the sign-making faculty in brutes; next I considered the language of tone and gesture as this is exhibited by man; then I proceeded to investigate the phenomena of articulation, the relation of tone and gesture to words; and, lastly, the psychology of speech. Not to overburden the present summary, I will neglect all the subordinate results of this analysis. The main results, however, were that the natural language of tone and gesture is identical wherever it occurs; but that even when it becomes conventional (as it may up to a certain point in brutes), it is much less efficient than articulate language as an agency in the construction of ideas; and, therefore, that the psychological line between brute and man must be drawn, not at language, or sign-making in general, but at that particular kind of sign-making which we understand by “speech.” Nevertheless, the real distinction resides in the intellectual powers; not in the symbols thereof. So that a man means, it matters not by what system of signs he expresses his meaning. In other words, although I endeavoured to prove that articulation must have been of unique service in developing these intellectual powers, I was emphatic in representing that, when once these powers are present, it is psychologically immaterial