The most dangerous madmen are those created by religion, and people whose aim is to disrupt society always know how to make good use of them on occasion.

If reason be a gift of Heaven, and we can say as much of faith, Heaven has certainly made us two gifts not only incompatible, but in direct contradiction to each other. In order to solve the difficulty, we are compelled to say either that faith is a chimera or that reason is useless.

As long as the centuries continue to unfold, the number of books will grow continually, and one can predict that a time will come when it will be almost as difficult to learn anything from books as from the direct study of the whole universe. It will be almost as convenient to search for some bit of truth concealed in nature as it will be to find it hidden away in an immense multitude of bound volumes.

Distance is a great promoter of admiration.

In general, children, like men, and men, like children, prefer entertainment to education.

Gentleness and peacefulness regulate our proceedings; theirs are dictated by fury. We employ reason, they accumulate faggots. They preach nothing but love, and breathe nothing but blood. Their words are humane, but their hearts are cruel.

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.