Ghost stories are always listened to and well received in private, but pitilessly disavowed in public. For my own part, ignorant as I am of the way in which the human spirit enters the world and the way in which he goes out of it, I dare not deny the truth of many such narratives.

The instruction of children should aim gradually to combine knowing and doing. Among all sciences mathematics seems to be the only one of a kind to satisfy this aim most completely.

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.

If an offender has committed murder, he must die. In this case, no possible substitute can satisfy justice. For there is no parallel between death and even the most miserable life, so that there is no equality of crime and retribution unless the perpetrator is judicially put to death.

The function of the true state is to impose the minimum restrictions and safeguard the maximum liberties of the people, and it never regards the person as a thing.

When a thoughtful human being has overcome incentives to vice and is aware of having done his bitter duty, he finds himself in a state that could be called happiness, a state of contentment and peace of mind in which virtue is its own reward.