A man should always have these two rules in readiness; the one, to do only whatever the reason of the ruling and legislating faculty may suggest for the use of men; the other, to change thy opinion, if there is any one at hand who sets thee right and moves thee from any opinion. But this change of opinion must proceed only from a certain persuasion, as of what is just or of common advantage, and the like, not because it appears pleasant or brings reputation.
And next thou must observe what thy nature requires so far as thou art a living being. And all this thou mayest allow thyself, if thy nature, so far as thou art a rational animal, shall not be made worse by it. But the rational animal is consequently also a political (social) animal. Use these rules, then, and trouble thyself about nothing else.
If any have offended against thee, consider first: What is my relation to men, and that we are made for one another... Remember these nine rules, as if thou hadst received them as a gift from the Muses, and begin at last to be a man while thou livest.