But if you are looking on anyone as a friend when you do not trust him as you trust yourself, you are making a grave mistake, and have failed to grasp sufficiently the full force of true friendship.

After friendship is formed you must trust, but before that you must judge.

Think for a long time whether or not you should admit a given person to your friendship.

Welcome him heart and soul, and speak as unreservedly with him as you would with yourself.