Pay attention to your enemies, for they are the first to discover your mistakes.
I am sadly afraid that I must have done some wicked thing.
Not to unlearn what you have learned is the most necessary kind of learning.
Royalty does good and is badly spoken of.
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 advantages of philosophy? That I am able to hold converse with myself.