There is a memorable dialog in Gladiator that contains a wealth of wisdom.

Marcus Aurelius: Will you accept this great honor that I have offered you?
Maximus: With all my heart, no.
Marcus Aurelius: Maximus... that is why it must be you.
Maximus: And Commodus?
Marcus Aurelius: Commodus is not a moral man. Commodus cannot rule. He must not rule.