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

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

Modern man was not meant to do his best work before forty but is by nature, and is becoming more so, an afternoon and evening worker.

Oneness with Nature is the glory of childhood oneness with childhood is the glory of the Teacher.

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. They have built all the roads, cities and machines in the world, written all the books, spoken all the words, and, in fact done everything that man has accomplished with matter. Character might be a sense defined as a plexus of motor habits.

Being an only child is a disease in itself.

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

Of all work-schools, a good farm is probably the best for motor development.

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.

Puberty for a girl is like floating down a broadening river into an open sea.

Normal children often pass through stages of passionate cruelty, laziness, lying and thievery.

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

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