The philosopher forms his principles on an infinity of particular observations. He does not confuse truth with plausibility, he takes for truth what is true, for false what is false, for doubtful what is doubtful, and probable what is probable. The philosophical spirit is thus a spirit of observation and accuracy.

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

You live as if you were destined to live forever, no thought of your frailty ever enters your head, of how much time has already gone by you take no heed. You squander time as if you drew from a full and abundant supply, so all the while that day which you bestow on some person or thing is perhaps your last. You have all the fears of mortals and all the desires of immortals… What foolish forgetfulness of mortality to defer wise resolutions to the fiftieth or sixtieth year, and to intend to begin life at a point to which few have attained.

The enjoyment of freedom which could be exercised without any motivation would be the real hallmark of a maniac.

When shall we see poets born? After a time of disasters and great misfortunes, when harrowed nations begin to breathe again. And then, shaken by the terror of such spectacles, imaginations will paint things entirely strange to those who have not witnessed them.

Scepticism is the first step toward truth.

All things must be examined, debated, investigated without exception and without regard for anyone's feelings... We must run roughshod over all these ancient puerilities, overturn the barriers that reason never erected, give back to the arts and sciences the liberty that is so precious to them.