[…] different languages make different classifications: some of them so unlike ours, so much less elaborate and complete, that their acquisition gives the eye and mind a very inferior training in distinguishing colors.
- Whitney (1875), a pag.20

[…] the acquisition of language is the adoption of certains classifications; herein consists a large share of its value as a means of training.
- Whitney (1875), a pag.78

Only the learned and experienced investigator […] can be trusted to push the work of classification safely to its extreme limits; and the classification of all human tongues is only attainable by the labors of a great number of investigators, each learned in his own special department. Nor has it been even thus by any means finished; yet much has been done toward it […].
- Whitney (1875), a pag.174