In a crystal we have clear evidence of the existence of a formative life principle, and though we cannot understand the life of a crystal, it is nonetheless a living being
My interest in science was always essentially limited to the study of principles.... That I have published so little is due to this same circumstance, as the great need to grasp principles has caused me to spend most of my time on fruitless pursuits.
To see others suffer does one good, to make others suffer even more: this is a hard saying but an ancient, mighty, human, all-too-human principle [....] Without cruelty there is no festival.