The background of my early thinking was a German home in which the ideals of the revolution of 1848 were a living force. My father, liberal, but not active in public affairs; my mother, idealistic, with a lively interest in public matters; the founder about 1854 of the kindergarten in my home town, devoted to science. My parents had broken through the shackles of dogma. My father had retained an emotional affection for the ceremonial of his parental home, without allowing it to influence his intellectual freedom