Never participate in the secrets of those above you; you think you share the fruit, and you share the stones - the confidence of a prince is not a grant, but a tax

No one demands more caution than a spy, and when someone has the skeleton key to minds, counter him by leaving the key of caution inside, on the other side of the keyhole.

I strive to be brief, and I become obscure.

Hear, see, and be silent.

Two kinds of people are good at foreseeing danger: those who have learned at their own expense, and the clever people who learn a great deal at the expense of others.

Know how to choose well. Most of life depends thereon. It needs good taste and correct judgment, for which neither intellect nor study suffices.

He that communicates his secret to another makes himself that other's slave.