Observe your enemies, for they first find out your faults.
Royalty does good and is badly spoken of.
As iron is eaten away by rust, so the envious are consumed by their own passion.
Not to unlearn what you have learned is the most necessary kind of learning.
The most useful piece of learning for the uses of life is to unlearn what is untrue.
We must not contradict, but instruct him that contradicts us; for a madman is not cured by another running mad also.