6. At first tragedies were brought on the stage as means of reminding men of the things which happen to them, and that it is according to nature for things to happen so, and that, if you are delighted with what is shown on the stage, you should not be troubled with that which takes place on the larger stage. For you see that these things must be accomplished thus, and that even they bear them who cry out, “O Cithaeron.” And, indeed, some things are said well by the dramatic writers, of which kind is the following especially:—"Me and my children if the gods neglect, This has its reason too."
And again,–"We must not chafe and fret at that which happens."
And,–"Life's harvest reap like the wheat's fruitful ear."
And other things of the same kind.
After tragedy the old comedy was introduced, which had a magisterial freedom of speech, and by its very plainness of speaking was useful in reminding men to beware of insolence; and for this purpose too Diogenes used to take from these writers.
But as to the middle comedy, which came next, observe what it was, and again, for what object the new comedy was introduced, which gradually sank down into a mere mimic artifice. That some good things are said even by these writers, everybody knows: but the whole plan of such poetry and dramaturgy, to what end does it look?
Source: The Thoughts of the Emperor Marcus Aurelius Antoninus by Marcus Aurelius Antoninus, translated by George Long