Adolescence as the time when an individual ‘recapitulates’ the savage stage of the race’s past.

The man of the future may, and even must, do things impossible in the past and acquire new motor variations not given by heredity.

All possible truth is practical. To ask whether our conception of chair or table corresponds to the real chair or table apart from the uses to which they may be put, is as utterly meaningless and vain as to inquire whether a musical tone is red or yellow. No other conceivable relation than this between ideas and things can exist. The unknowable is what I cannot react upon. The active part of our nature is not only an essential part of cognition itself, but it always has a voice in determining what shall be believed and what rejected.

Adolescence is a new birth, for the higher and more completely human traits are now born.

The teens are emotionally unstable and pathic. It is a natural impulse to experience hot and perfervid psychic states, and it is characterized by emotionalism. We see here the instability and fluctuations now so characteristic. The emotions develop by contrast and reaction into the opposite.

Every theory of love, from Plato down teaches that each individual loves in the other sex what he lacks in himself.

.. every step of the upward way is strewn with wreckage of body, mind, and morals.