It will be noticed that we have used the terms "dialect" and "language" indifferently and interchangeably, in speaking of any given tongue; and it will also have been made plain, I trust, by the foregoing exposition how vain would be the attempt to establish a definite and essential distinction between them, or give precision to any of the other names which indicate the different degrees of diversity among related tongues. No form of speech, living or dead, of which we have any knowledge, was not or is not a dialect, in the sense of being the idiom of a limited community, among other communities of kindred but somewhat discordant idiom; none is not truly a language, in the sense that it is the means of mutual intercourse of a distinct portion of mankind, adapted to their capacity and supplying their needs. The whole history of spoken language, in all climes and all ages, is a series of varying and successive phases; external circumstances, often accidental, give to some of these phases a prominence and importance, a currency and permanence, to which others do not attain; and according to their degree of importance we style them idiom, or patois, or dialect, or language. To a very limited extent, natural history feels the same difficulty in establishing the distinction between a "variety" and a "species:" and the difficulty would be not less pervading and insurmountable in natural than in linguistic science, if, as is the case in language, not only the species, but even the genera and higher groups of animals and plants were traceably descended from one another or from common ancestors, and passed into each other by insensible gradations. Transmutation of species in the kingdom of speech is no hypothesis, but a patent fact, one of the fundamental and determining principles of linguistic study.
