"What then makes a beautiful human being? Is it not the possession of human excellence? And do you, then, if you wish to be beautiful, young man, labour at this, the acquisition of human excellence. But what is this? Observe whom you yourself praise, when you praise many persons without partiality: do you praise the just or the unjust? 'The just.' Whether do you praise the even-tempered or the undisciplined? 'The even-tempered.' And the self-controlled or the uncontrolled? 'The self-controlled.' If, then, you make yourself such a person, you will know that you will make yourself beautiful: but so long as you neglect these things, you must be ugly, even though you contrive all you can to appear beautiful."
(Epictetus, Discourses 3.1.6ff)
