Nature in denying us perennial youth has at least invited us to become unselfish and noble.

The brute necessity of believing something so long as life lasts does not justify any belief in particular.

The world is a perpetual caricature of itself; at every moment it is the mockery and the contradiction of what it is pretending to be.

It takes a wonderful brain and exquisite senses to produce a few stupid ideas.

The body is an instrument, the mind its function, the witness and reward of its operation.

The hunger for facile wisdom is the root of all false philosophy.

Progress, far from consisting in change, depends on retentiveness. Those who cannot remember the past are condemned to repeat it.