'If Locke is right in considering the having of general ideas as the distinguishing feature between man and brutes, and, if we ourselves are right in pointing to language as the one palpable distinction between the two, it would seem to follow that language is the outward sign and realization of that inward faculty which is called the faculty of abstraction, but which is better known to us by the homely name of reason. 'Let us now look back to the result of former lectures. It was this: After we had explained everything in the growth of language that can be explained, there remained in the end, as the only inexplicable residuum, what we called _roots_. These roots formed the constituent elements of all languages.... What, then, are these roots?' Two theories have been started to solve this problem: the Onomatopoetic, according to which roots are imitations of sounds; and the Interjectional, which regards them as involuntary ejaculations. Having discussed these theories, and taken the position that, although there are roots in every language which are respectively imitations of sounds and involuntary exclamations, it is, nevertheless, impossible to regard any considerable number of roots, and much less, all roots, as originating from these sources, the distinguished Philologist announces as the true theory, that every root 'expresses a general, not an individual, idea;' just the opposite of what he deems would be the case if the Onomatopoetic and Interjectional theories explained the origin of speech. Some paragraphs are then devoted to the examination of the merits of a controversy which has existed among philosophers as to