Wisdom from the Early Stoics, Zeno of Citium 64

The reason why the Stoics characterize the perfect good as beautiful is that it has in full all the "factors" required by nature or has perfect proportion. 

Of the beautiful there are, they say, four species, namely, what is just, courageous, orderly, and wise; for it is under these forms that fair deeds are accomplished. 

Similarly there are four species of the base or ugly, namely, what is unjust, cowardly, disorderly, and unwise. 

By the beautiful is meant properly and in an unique sense that good which renders its possessors praiseworthy, or briefly, good which is worthy of praise; though in another sense it signifies a good aptitude for one's proper function; while in yet another sense the beautiful is that which lends new grace to anything, as when we say of the wise man that he alone is good and beautiful. 

—Diogenes Laërtius, 7.100 

IMAGE: Anonymous Italian, Truth and Beauty (c. 1700)