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.

This splendid subject [mathematics], queen of all exact sciences, and the ideal and norm of all careful thinking.

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

Muscles are in a most intimate and peculiar sense the organs of the will.

Constant muscular activity was natural for the child, and, therefore, the immense effort of the drillmaster teachers to make children sit still was harmful and useless.

There is no more wild, free, vigorous growth of the forest, but everything is in pots or rows like a rococo garden... The pupil is in the age of spontaneous variation which at no period of life is so great. He does not want a standardized, overpeptonized mental diet. It palls on his appetite.

Precisely what menstruation is, is not yet very well known.