Great question. In a sense, the claim (or assumption) that there is a link between a major aesthetic category beauty and ethics / morality goes back to Plato. From a Platonic point of view, is some act is wicked, it is evil, and if some act is ethical it is beautiful (or, in difficult matters), the least ugly act possible. The close link between beauty and moral goods and virtues continues on up through the Renaissance. Today, there is disagreement about the extent to which ethics and aesthetics conflict; some argue that the two realms are altogether different (a standard claim by those who believe in the separation of ethics and aesthetics is that Leni Riefenstahl's film Triumph of the Will is an excellent film aesthetically but morally horrifying) whereas some of us still seek to bring them together. You can get a good overview of the state of play in this debate in the collection Aesthetics and Ethics edited by Jerrold Levinson (Cambridge University Press). In terms of systematic defenses of the link between aesthetics and ethics, you might check out the enigmatic but highly stimulating work of Guy Sircello.
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Are there any extensive philosophical examinations of a link between aesthetics and ethics? I had heard that Nietzsche and Rousseau, for example, argued that the two were fundamentally linked. Specifically, I am curious as to whether any philosophers have advanced the position that ethics and morality are sub-fields of aesthetics (an "Aesthetics of Human Behavior", if you will).