Examine men's ruling principles, even those of the wise, what kind of things they avoid, and what kind they pursue.
Constantly observe who those are whose approbation thou wishest to have, and what ruling principles they possess. For then thou wilt neither blame those who offend involuntarily, nor wilt thou want their approbation, if thou lookest to the sources of their opinions and appetites.
Alexander and Gaius and Pompeius, what are they in comparison with Diogenes and Heraclitus and Socrates? For they were acquainted with things, and their causes (forms), and their matter, and the ruling principles of these men were the same. But as to the others, how many things had they to care for, and to how many things were they slaves?