Vegetarian food leaves a deep impression on our nature. If the whole world adopts vegetarianism, it can change the destiny of humankind.

Weakness of attitude becomes weakness of character.

Mathematics deals exclusively with the relations of concepts to each other without consideration of their relation to experience.

We must dedicate our lives to drying up the source of war: ammunition factories.

Science can only ascertain what is, but not what should be, and outside of its domain value judgements of all kinds remain necessary.

The only real valuable thing is intuition. The intellect has little to do on the road to discovery

By academic freedom I understand the right to search for truth and to publish and teach what one holds to be true. This right also implies a duty: one must not conceal any part of what one has recognized to be true.