Open your mind before your mouth

High thoughts must have high language.

Meton (astronomer in 5th century BC): With the straight ruler I set to work To make the circle four-cornered .

You're mistaken; men of sense often learn much from their enemies. Prudence is the best safeguard. This principle cannot be learnt from a friend: but an enemy extorts it immediately. It is from their foes and not their friends, that cities learn the lesson of building high walls and ships of war. And this lesson saves their children, their homes, and their properties.

The wise learn many things from their enemies.

Thou shouldst not decide until thou hast heard what both have to say.

The old are in a second childhood.