We have followed Reid so far in his study of language, because it is along this way that he came to form the concepts that were to serve him as a key for his all-important findings in the realm of sense-experience. These are the concepts which bear on the connexion between the sign and the thing signified; the distinction between the artificial and the natural state of language; and the disappearance of certain primeval human capacities for experience, of which Reid says that they are brought by the child into the world, but fade as his intellectual capacities develop.