Aristotle, Rhetoric
J. H. Freese, Ed.

[18] We will define anger when we come to speak of the emotions.¹ Desire is the cause of things being done that are apparently pleasant. The things which are familiar and to which we have become accustomed are among pleasant things; for men do with pleasure many things which are not naturally pleasant, when they have become accustomed to them.

In short, all things that men do of themselves either are, or seem,
good or pleasant; and since men do voluntarily what they do of themselves, and involuntarily what they do not, it follows that all that men do voluntarily will be either that which is or seems good, or that which is or seems pleasant. For I reckon among good things the removal of that which is evil or seems evil, or the exchange of a greater evil for a less, because these two things are in a way desirable; in like manner, I reckon among pleasant things the removal of that which is or appears painful, and the exchange of a greater pain for a less. We must therefore make ourselves acquainted with the number and quality of expedient and pleasant things.