He who knows not and knows not that he knows not is an incorrigible fool.

Only a fool can't be fooled.

He that cannot reason is a fool, He that will not a bigot, He that dare not a slave.

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.

A fool is an automaton, a machine with springs which turn him about always in one manner, and preserve his equilibrium. He is ever the same, and never changes. If you have seen him once you have seen him at every moment and period of his life. He is at best but as the lowing ox or the whistling blackbird. He is fixed and obstinate, I may say, by nature. What appears least in him is his soul; that has neither activity nor energy; it reposes.

He that cannot reason is a fool. He that will not is a bigot. He that dare not is a slave.

what's so beautiful about a fool is that a fool never knows when to give up

According to mainstream non-religious sources, a fool is one who too readily accepts improbable assertions from questionable sources on insufficient evidence. So it is no wonder that the Bible and the Qur’an both use the opposite definition, so that the wise are called foolish and only fools are wise. By definition, one would have to be a fool to be fooled by either book. As for “putting things right”, the only way to do that is to identify unsupported assertions and examine what the facts really indicate, and that always goes against faith.

Fools are more hard to conquer than persuade.

A fool is someone whose pencil wears out before its eraser does.

A fool is twice a fool who tries to conceal it.

Only a fool never changes his mind.

Fools are determined to be fools. Trying to stop them from being so is futile.

The fool is willing to pay for anything but wisdom. No man buys that of which he supposes himself to have an abundance already.