If the fool would persist in his folly he would become wise.

The fool who persists in his folly will become wise.

The fool who knows he is a fool is that much wiser.

Even a fool may be wise after the event.

Fools learn wisdom through misfortune.

Whoever among you thinks himself wise must become a fool to be truly wise

Let a fool be made serviceable according to his folly.

Answer a fool according to his folly” (Proverbs 26:4).

the wise may be instructed by a fool

If any man among you seemeth to be wise in this world, let him become a fool, that he may be wise.

He who lives without folly is not as wise as he may think.

The fool doth think he is wise, yet it is the wise man that knows himself to be the fool As You Like It, Act 5, Scene 1

What the wise man does in the beginning, the fool does in the end

Progress is a possibility for the animal: it can be broken in, tamed and trained; but it is not a possibility for the fool, because the fool thinks he has nothing to learn. It is his place to dictate to others and put them right, and so it is impossible to reason with him. He will laugh you to scorn in saying that what he does not understand is not a meaningful proposition. 'Why don't I understand it, then?', he asks you, with marvellous impudence. To tell him it is because he is a fool would only be taken as an insult, so there is nothing you can say in reply. Everybody else sees it quite clearly, but he will never realize it.<p>Here then, at the outset, is a potent secret which is inaccessible to the majority of people; a secret which they will never guess and which it would be useless to tell them: the secret of their own stupidity.