"You have all heard," says Sir William Hamilton, "of the process of tunnelling through a sandbank. In this operation it is impossible to succeed unless every foot, nay, almost every inch of our progress be secured by an arch of masonry before we attempted the excavation of another. Now language is to the mind precisely what the arch is to the tunnel. The power of thinking and the power of excavation are not dependent on the words in the one case or on the mason-work in the other; but without these subsidiaries neither could be carried on beyond its rudimentary commencement. Though, therefore, we allow that every movement forward in language must be determined by an antecedent movement forward in thought, still, unless thought be accompanied at each point of its evolutions by a corresponding evolution of language, its further development is arrested." Man has evolved an articulate language, whereas the lower animals seem to be without one. Man, therefore, has far outstripped them in reasoning faculty as well as in power of expression. This, however, does not bar the communications which the lower animals make to one another from possessing all the essential characteristics of language, and, as a matter of fact, wherever we can follow them we find such communications effectuated by the aid of arbitrary symbols covenanted upon by the living beings that wish to communicate, and persistently associated with certain corresponding feelings, states of mind, or material objects. Human language is nothing more than this in principle, however much further the principle has been carried in our own case than in that of the lower animals. This being admitted, we should infer that the thought or reason on which the language of men and animals is alike founded differs as between men and brutes in degree but not in kind. More than this cannot be claimed on behalf of the lower animals, even by their most enthusiastic admirer. The Deadlock in Darwinism: Part I {245}