Every single language has […] its own peculiar framework of established distinctions, its shapes and forms of thought, into which, for the human being who learns that language as his “mother-tongue”, is cast the content and product of his mind, his store of impressions, however acquired, his experience and knowledge of the world. This is what is sometimes called the “inner form” of language- the shape and cast of thought, as fitted to a certain body of expression. But it comes as the result of external influence; it is an accompaniment of the process by which the individual acquires the body of expression itself; it is not a product of his internal forces, in their free and undirected workings; it is something imposed from without.
- Whitney (1875), a pag.21-22

The sum of what all the individual speakers contribute to the common store of thought and knowledge by original work has to be worked into the “inner form” of their language along with and by means of some alteration in its outer form.
- Whitney (1875), a pag.35

When we first take hold of an additional language, we cannot help translating its signs into those we already know; the peculiarities of its “inner form,” the non-identity and incommensurability of its shaped and grouped ideas with those of our native speech, escape our notice.
- Whitney (1875), a pag.23-24