Progress is impossible without change, and those who cannot change their minds cannot change anything.

You cannot be a hero without being a coward.

The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.

The power of accurate observation is commonly called cynicism by those who have not got it.

All progress means war with society.

Those who do not know how to live must make a merit of dying.