Men are so necessarily mad, that not to be mad would amount to another form of madness.

All men are mad in some way or the other;

Men will always be mad, and those who think they can cure them are the maddest of all.

Men can be brilliant and strong, they whispered to one another. But men can be mad, as well. And the mad ones can ruin the world.

A great many men are mad, and no one knows it. They do not know it themselves

All men are mad in some way or another, and inasmuch as you deal discreetly with your madmen, so deal with God's madmen too, the rest of the world.

To obtain a man's opinion of you, make him mad.

Men have been so mad as to believe that God is pleased by harmony.

He may be mad, but there's method in his madness. There nearly always is method in madness. It's what drives men mad, being methodical.

A man has to be a bit mad [...]. That's the best thing about him.

Man is certainly stark mad; he cannot make a worm, and yet he will be making gods by dozens.

To say a man does mad things because he is mad is merely unintelligent and stupid. A madman is as logical and reasoned in his action as a sane man — given his peculiar biased point of view. For example, if a man insists on going out and squatting about in nothing but a loin cloth his conduct seems eccentric in the extreme. But once you know that the man himself is firmly convinced that he is Mahatma Gandhi, then his conduct becomes perfectly reasonable and logical.

Madness breeds madness.

It was pretty clear that he was mad, for madness means just this dislocation of the modes of thought which mortals have agreed upon as necessary to keep the world together.