Thus we may lay it down as a general doctrine or well-substantiated principle of philological research, that “Language begins with sentences; not with single words;”[225] or that originally every word in and of itself required to convey a meaning, after the manner of the early utterances of children. “The sentence is the only unit which language can know, and the ultimate starting-point of all our linguistic researches.... If the sentence is the unit of significant speech, it is evident that all individual words must once have been sentences; that is to say, when first used they must each have implied or represented a sentence.”[226] “The making of words as distinct from sentences was a long and laborious process, and there are many languages, like those of North America, in which the process has hardly yet begun. A dictionary is the result of reflection, and ages must elapse before a language can enter upon its reflective stage.”[227] Or, to give only one more quotation, as Professor Max Müller says, “it is difficult for us to think in Chinese, or in any radical language, without transferring to it our categories of thought. But if we watch the language of a child, which is really Chinese spoken in English, we see that there is a form of thought, and of language, perfectly rational and intelligible to those who have studied it, in which, nevertheless, the distinction between noun and verb, nay, between subject and predicate, is not yet realized.”[228] Starting, then, from this undifferentiated condition of language, let us next see how the “parts of speech” became evolved.