The most necessary learning is that which unlearns evil.

We must not contradict, but instruct him that contradicts us; for a madman is not cured by another running mad also.

Not to unlearn what you have learned is the most necessary kind of learning.

As rust corrupts iron, so envy corrupts man.

There are only two people who can tell you the truth about yourself - an enemy who has lost his temper and a friend who loves you dearly.

We weed out the darnel from the corn and the unfit in war, but do not excuse evil men from the service of the state.

The most useful piece of learning for the uses of life is to unlearn what is untrue.