Organs, faculties, powers, capacities, or whatever else we...

Organs, faculties, powers, capacities, or whatever else we call them; grow by use and diminish from disuse, it is inferred that they will continue to do so. And if this inference is unquestionable, then is the one above deduced from it-that humanity must in the end become completely adapted to its conditions-unquestionable also. Progress, therefore, is not an accident, but a necessity.