[…] all the languages in question [Romanic and Germanic tongues] are the divaricated representatives of a single tongue, spoken somewhere and some when in the past by a single limited community, by the spread and dispersion of which all its discordances have in the course of time grown up.
- Whitney (1875), a pag.174

[…] correspondences in the material of different languages, if existing in measure and kind beyond what can be accounted for as the result of accident or borrowing, is explainable only as due to the separate tradition of an originally common tongue, a tradition which preserved a part of the original usages, while it modified or discarded other parts, or introduced what was new, to such an extent as to obscure, and perhaps, even to hide, the evidences of former connection.
- Whitney (1875), a pag.179-180

[…] the individual learns his language, obtaining the spoken signs of which it is made up by imitation from the lips of others, and shaping his conceptions in accordance with them. It is thus that every language is maintained in life; if this process of tradition, by teaching and learning, were to cease in any tongue upon earth, that tongue would at once become extinct.
- Whitney (1875), a pag.32

Its [of science of language] foundations have been laid deep and strong in the thorough analysis of many of the most important human tongues, and the careful examination and classification of nearly all the rest.
- Whitney (1875), a pag.5

There is no human tongue which is destitute of the expression of form […].
- Whitney (1875), a pag.222