From a discussion in the shoutbox. Add your citations here.
Given that while some things are pleasant by nature (some of these without qualification, others with reference to particular types both of animals and of human beings), other things are not, but come to be pleasant whether because of disablement or through habituation, or again because of a natural lack of quality, in relation to each of these kinds of thing too one can observe dispositions of a corresponding sort. I mean the brutish ones ... These dispositions are brutish, but some result from diseases (and in some cases from madness, as with the man who sacrificed and ate his mother, or the one who ate his fellow slave's liver), while others are morbid dispositions resulting from habituation, e.g. pulling out one's hair or chewing on one's nails, or again on charcoal or earth, or, to add another example, the disposition to sexual activity with other males; for in some cases the dispositions in question occur naturally, while in others they result from habituation, as with those who are abused from childhood on. Where nature is responsible, then, no one would call these types un-self-controlled, any more than one would call women un-self-controlled because they have the passive rather than the active role in copulation... - Aristotle, Nicomachean Ethics VII.5.1148b25