What a person thinks on his own without being stimulated by the thoughts and experiences of the other people is even in the best case rather paltry and monotonous.

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

While it is true that an inherently free and scrupulous person may be destroyed, such an individual can never be enslaved or used as a blind tool.

The creative principle [of science] resides in mathematics.

We cannot despair of humanity, since we ourselves are human beings.

The world is a dangerous place to live; not because of the people who are evil, but because of the people who don't do anything about it.

Learn from yesterday, live for today.