This cumulative character of the signs of relationship, the uncertain value of any single item, and the need of historical evidence to support their interpretation, set limits to the reach and competence of linguistic investigation.
- Whitney (1875), a pag.267-268

[…] relationship in language, as in genealogy, is a thing of degree, and for the same reason.
- Whitney (1875), a pag.170

[…] the great principle that genuine correspondences, of whatever degree, between the words of different languages, are to be interpreted as the result of derivation from one original: relationship, in words as in men, implies a descent from a common ancestor.
- Whitney (1875), a pag.169

Certain elements in English are of common descent with elements in the Romanic and in many other of the world’s languages; they have been handed over from the tradition of one people into that of another; and though there is so far a community of tradition, it does not imply general relationship of the languages.
- Whitney (1875), a pag.170