Each department of knowledge passes through three stages. The theoretic stage; the theological stage and the metaphysical or abstract stage.

Men are not allowed to think freely about chemistry and biology: why should they be allowed to think freely about political philosophy?

Demography is destiny.

Every science consists in the coordination of facts; if the different observations were entirely isolated, there would be no science.

Ideas govern the world, or throw it into chaos.

Know yourself to improve yourself.

The dead govern the living.

The only real life is the collective life of the race; individual life has no existence except as an abstraction.

The word 'right' should be excluded from political language, as the word 'cause' from the language of philosophy.

To understand a science, it is necessary to know its history.

Indeed, every true science has for its object the determination of certain phenomena by means of others, in accordance with the relations which exist between them.