Plutarch Quomodo quis suos in virtute sentiat profectus 2

[2] Rightly has it been said: But those who do not adjust their tenets to fit the facts, but rather try to force the facts into an unnatural agreement with their own assumptions, ² have filled philosophy with a great number of difficulties, of which the greatest is that which would assign all men to a general category of badness with the single exception of the absolutely perfect man; the result of which is to make a puzzle out of what we call progress, since it falls but little short of the uttermost foolishness, and represents men who have been released by it from all kinds of passions and weaknesses as living in a state of equal wretchedness with those who have not yet been freed from a single one of the worst evils. Now these men really refute themselves when, in their lectures, they put the wrongdoing of Aristeides on an equality with that of Phalaris, and the cowardice of Brasidas on an equality with that of Dolon, and the hard-hearted attitude of Plato as actually not differing at all from that of Meletus; whereas in their life and practice they show an aversion for these latter men and avoid them as ruthless, but the former they seem to think are men of great worth, for they cite them with confidence in the most important matters.

[2] It is very good advice, Measure the stone by your rule, and not your rule by the stone. But the Stoics have not observed it; for they, not applying principles to things, but forcing things which have no foundation of agreement in nature to agree to their principles, have filled philosophy with a number of difficulties. One of the hardest to be solved is this, that all men whatsoever (except him who is absolutely perfect) are equally vicious. Hence is that enigma, called progress or proficiency, which, though it has puzzled the learned to solve, is in my opinion very foolish; for it represents those that have advanced a little, and are partly free from inordinate passions and distempers of mind, to be as unhappy as those that are guilty of the most heinous enormities. And indeed the assertion is so absurd, that their own actions are enough to confute it; for while they maintain in their schools that Aristides and Phalaris are equally unjust, that Brasidas and Dolon are equal cowards, and that Plato and Meletus are equally senseless, still in all affairs of life they seem to reject and avoid the latter of these, as too harsh and severe to be softened into compliance, but credit and quote the former in all their writings, as persons of extraordinary worth and esteem. This is what the Stoics assert.