When we know to read our own hearts, we acquire wisdom of the heartsof others.

A nation which thinks that it is belief in God and not good law which makes people honest does not seem to me very advanced.

Only the bad man is alone.

The arbitrary rule of a just and enlightened prince is always bad. His virtues are the most dangerous and the surest form of seduction: they lull a people imperceptibly into the habit of loving, respecting, and serving his successor, whoever that successor may be, no matter how wicked or stupid.

I picture the vast realm of the sciences as an immense landscape scattered with patches of dark and light. The goal towards which we must work is either to extend the boundaries of the patches of light, or to increase their number. One of these tasks falls to the creative genius; the other requires a sort of sagacity combined with perfectionism.

A thing is not proved just because no one has ever questioned it. What has never been gone into impartially has never been properly gone into. Hence scepticism is the first step toward truth. It must be applied generally, because it is the touchstone.

It seems to me that if one had kept silence up to now regarding religion, people would still be submerged in the most grotesque and dangerous superstition ... regarding government, we would still be groaning under the bonds of feudal government ... regarding morals, we would still be having to learn what is virtue and what is vice. To forbid all these discussions, the only ones worthy of occupying a good mind, is to perpetuate the reign of ignorance and barbarism.