Man must strive, and striving he must err.

There is nothing more frightful than for a teacher to know only what his scholars are intended to know.

Most man only care for science so far as they get a living by it, and that they worship even error when it affords them a subsistence.

The one who acts is always without conscience; nobody has a conscience but the contemplative person.

Man... knows only when he is satisfied and when he suffers, and only his sufferings and his satisfactions instruct him concerning himself, teach him what to seek and what to avoid. For the rest, man is a confused creature; he knows not whence he comes or whither he goes, he knows little of the world, and above all, he knows little of himself.

The solution of every problem is another problem

Happy contractedness of youth, nay, of mankind in general, that they think neither of the high nor the deep, of the true nor the false, but only of what is suited to their own conceptions.