God, freedom, and immortality are untenable in the light of pure reason.

I assert that, in any particular natural science, one encounters genuine scientific substance only to the extent that mathematics is present.

All our knowledge begins with the senses...

Reason can never prove the existence of God.

The greatest problem for the human species, the solution of which nature compels him to seek, is that of attaining a civil society which can administer justice universally.

Parents usually educate their children merely in such a manner than however bad the world may be, they may adapt themselves to its present conditions. But they ought to give them an education so much better than this, that a better condition of things may thereby be brought about by the future.

Even philosophers will praise war as ennobling mankind, forgetting the Greek who said: 'War is bad in that it begets more evil than it kills.'