In ethnological philology, as in natural history, descent is the paramount fact; and without asking how far the value thus given to it is liable to be refined on, we leave it, in each science, as we find it, until some future investigator shall have shewn that either for a pair of animals not descended from a common stock, or for a pair of languages not originating from the same mother-tongue, a greater number of general propositions can be predicated than is the case with the two most dissimilar instances of either an animal or a language derived from a common origin.
Languages are allied just in proportion as they were separated from the same language at the same epoch.
The same epoch.—The word epoch is an equivocal word, and it is used designedly because it is so. Its two meanings require to be indicated, and, then, it will be necessary to ask which of them is to be adopted here.
The epoch, as a period in the duration of a language, may be simply chronological, or it may be philological, properly so called.
The space of ten, twenty, a hundred, or a thousand years, is a strictly chronological epoch. The first fifty years after the Norman conquest is an epoch in the history of the English language; so is the reign of Henry the Third, or the Protectorship of Oliver Cromwell. A definite period of this sort is an epoch in language, just as the term of twenty or thirty years is an epoch in the life of a man.
On the other hand, a period that, chronologically speaking, is indefinite, may be an epoch. The interval between one change and an other, whether long or short, is an epoch. The duration of English like the English of Chaucer, is an epoch in the history of the English language; and so is the duration of English like the English of the Bible translation. For such epochs there are no fixed periods. With a language that changes rapidly they are short; with a language that changes slowly they are long.
Now, in which of these two meanings should the word be used in ethnographical philology? The answer to the question is supplied by the circumstances of the case, rather than by any abstract propriety. We cannot give it the first meaning, even if we wish to do so. To say in what year of the duration of a common mother-tongue the Greek separated from the stock that was common to it and to the Latin is an impossibility; indeed, if it could be answered at once, it would be a question of simple history, not an inference from ethnology: since ethnology, with its palæontological reasoning from effect to cause, speaks only where history, with its direct testimony, is silent.
We cannot, then, in ethnological reasoning, get at the precise year in which any one or two languages separated from a common stock, so as to say that this separated so long before the other.
The order, however, of separation we can get at; since we can infer it from the condition of the mother-tongue at the time of such separation; this condition being denoted by the condition of the derived language.
Hence the philological epoch is an approximation to the chronological epoch, and as it is the nearest approximation that can possibly be attained, it is practically identical with it, so that the enunciation of the principle at which we wish to arrive may change its wording, and now stand as follows,—Languages are allied, just in proportion as they were separated from the same language in the same stage.