Until my current reading of Aristotle's ethical writings, I had never noticed the connection he draws between ethics and beauty. No, not the surface beauty of physical good looks with which people are so obsessed these days, but the desire for true beauty: to have a beautiful character, to perform beautiful actions, to live a beautiful inner and outer life. Indeed, he frequently argues that an action is not truly ethical if it is not done for the sake of beauty. For example, someone who does something outwardly courageous only for the sake of social conformity does a good thing but not for the right reasons, whereas someone who performs the same act because it is a beautiful thing to do is in a higher ethical realm.
While trying to understand this idea, I got to thinking about Aristotle's so-called "doctrine of the mean", and specifically about a better way to translate his term "mesotes" (which is invariably translated as "the mean"). To stay with the example of courage, according to Aristotle the middle way between rashness and cowardice is courage. The rash person underestimates the dangers of a particular situation, whereas the coward exaggerates them; by contrast, the courageous person accurately perceives the dangers and therefore fears what deserves to be feared. Similarly for an emotion like anger - the irascible person gets angry on the wrong occasions and with the wrong people, is too quick to anger, etc. But Aristotle does not say that anger is a bad emotion, and in this way differs from those who claim that anger is a sin (Christianity) or an emotion to be avoided entirely (Epicureanism); instead he says that there is such a thing as justified anger, and that people who never get angry even when it is justified also miss the mark.
Thus I see "the mean" as a kind of dynamic, natural balance between too much and too little. And balance can be beautiful: think of a gymnast arched on the balance beam, or a dancer poised to make a pirouette, or a baseball shortstop finishing a double play at second base. Balance is also a matter of being well-proportioned, and according to Aristotle an excellence of character such as courage or generosity is a stable state of being to produce proportionate responses based on true understandings (a kind of disposition for "justified true emotion", if you will).
One further aspect of ethical beauty is related to an odd little side comment Aristotle makes in the Nicomachean Ethics about physical beauty: that small people can be cute but they can't be beautiful because they're simply not big enough. Whether or not this strange notion was common in ancient Greece, it might be connected to Aristotle's idea of greatness of soul (megalopsuchia): only people who achieve all-around excellence of character, who truly thrive as human beings, can have ethical beauty; by contrast, people who don't aim as high might be neat and orderly and even admirable in their own less morally ambitious way, but according to Aristotle they're not ethically beautiful.