Thus, operations in the physical world which certainly do not look as if they were the work of intelligence, as we understand it, are seen to be closely paralleled by transactions in the history of man’s social life. The development of life, in fact, is carried forward when the plane of human consciousness is reached on just the same lines as those which prevailed on the vegetable and the animal plane: there is no breach of continuity in the broad outlines of evolutionary progress. It is difficult to over-estimate the significance of this fact.
Perhaps nothing that man has evolved is so purely a work of mind as Language. Here, the analogy with the phenomena of physical evolution is very close and very illuminating. As in nature, the ultimate origins are obscure—we can only form hypotheses as to how language came to arise from the cries of animals, as we can only form hypotheses how life arose from the play of molecular forces. But when both are once established on the earth we see in them the same general features—unity, in a few leading types, branching out into infinite modifications in subordinate groups. Greek, Erse, German, Russian, Sanskrit are all Aryan tongues and have all a common ancestry. They differ widely among each other, but all alike are marked off from the Semitic or the Mongolian families. So a man, a snake, a bear, a fish are all vertebrates, and belong to a type essentially distinct from that of a lobster or a snail. As in nature, we find all stages of development existing at the same time—some lines of development show a rapid advance, some a very slow one. Some types have, in both cases, perished completely—there are fossil languages as there are fossil species. A new invention, an advance _per saltum_, without the utilization of existing constituents, is almost as rare in the evolution of language as in that of species. Just as the lung is developed from the swim-bladder, so the human mind, in the development of language, takes hold of whatever existing form will suit its purpose and transforms it to another end, as when it takes a word for ‘breath’ and makes it ‘spirit.’ There are laws governing the development of root-forms, linguistic or physical, in various different orders or species. The same osseous framework yields us in one class of animal a hand, in another a hoof, in another a paw, in another (as in bats) a wing. So in language the same root yields us the words, in different languages, for _shining_, _showing_, _speaking_, _proving_, _a face_, _a story_, _whiteness_. Another gives us, _young_, a _stepmother_, a certain _musical string_, a _messenger_.[102] Contrariwise we see both in nature and in language forms which have grown from entirely different roots into a close external and functional similarity. What unlearned observer would suspect that a whale was not a fish, and that it descends from a furry land animal with four legs, or that the Latin _Deus_ and the Greek _Theos_ with their perfect identity of meaning and their almost perfect identity of sound have probably a widely divergent etymological pedigree?[103]