Nicomachean Ethics III.10

After courage let us speak of temperance; for these seem to be the virtues of the irrational parts. We have said that temperance is a mean with regard to pleasures (for it is less, and not in the same way, concerned with pains); self-indulgence also is manifested in the same sphere.

'The virtues of the irrational parts' of the soul, that is; but of course the virtues are not themselves part of the irrational part of the soul. They are the rational parts of the soul that control the irrational parts. Courage, as you have read several times now, is concerned with fear of pains to include wounds and death; temperance, principally with pleasures not to be over-indulged. 

Aquinas' promotion of temperance over courage makes sense even on Aristotle's own terms when you remember that Aquinas pointed out that most people are more motivated by pleasure than pain; recall the talk about Helen at the gates. 

Now, therefore, let us determine with what sort of pleasures they are concerned. We may assume the distinction between bodily pleasures and those of the soul, such as love of honour and love of learning; for the lover of each of these delights in that of which he is a lover, the body being in no way affected, but rather the mind; but men who are concerned with such pleasures are called neither temperate nor self-indulgent.

Indeed, the love of seeking that most worthy of honor is magnanimity, which is going to prove to be the capstone and crown of virtue. So: the high pleasures of the soul, especially to include living in a way that is most worthy of honor, should not be tempered but embraced.

There are other things people find pleasant that should not be, even though they are not bodily pleasures:

Nor, again, are those who are concerned with the other pleasures that are not bodily; for those who are fond of hearing and telling stories and who spend their days on anything that turns up are called gossips, but not self-indulgent, nor are those who are pained at the loss of money or of friends.

The Stoics might suggest that allowing yourself to be pained at the loss of money or friends is irrational, but grief over the loss of friends falls within Aristotle's quite large concession to friendship as part of the good life. Marcus Aurelias would remind you that you always knew your friends were mortal; but for Aristotle, life without friends is much impoverished because it degrades the life of one's own mind by removing another self in whose good you can also find happiness, which is the end of ethics.

Temperance must be concerned with bodily pleasures, but not all even of these; for those who delight in objects of vision, such as colours and shapes and painting, are called neither temperate nor self-indulgent; yet it would seem possible to delight even in these either as one should or to excess or to a deficient degree.

And so too is it with objects of hearing; no one calls those who delight extravagantly in music or acting self-indulgent, nor those who do so as they ought temperate.

Nor do we apply these names to those who delight in odour, unless it be incidentally; we do not call those self-indulgent who delight in the odour of apples or roses or incense, but rather those who delight in the odour of unguents or of dainty dishes; for self-indulgent people delight in these because these remind them of the objects of their appetite. And one may see even other people, when they are hungry, delighting in the smell of food; but to delight in this kind of thing is the mark of the self-indulgent man; for these are objects of appetite to him.

You may note the oddity of Aristotle referring so much to the common judgment: 'no one calls...' is argumentum ad populum. Aristotle was not concerned with what would later come to be called the informal fallacies; his considerations on logic generally point at formal logic, which isn't appropriate to ethics (EN I.3 again). He discusses the issue somewhat in the Rhetoric, especially in Book I, but there he is talking about enthymemes rather than strict logical arguments. "However, where the general premise of a syllogism is supposed to be true, making the subsequent deduction necessary, the general premise of an enthymeme is merely probable, which leads only to a tentative conclusion," thus making them proper for ethical/political arguments. 

Nor is there in animals other than man any pleasure connected with these senses, except incidentally. For dogs do not delight in the scent of hares, but in the eating of them, but the scent told them the hares were there; nor does the lion delight in the lowing of the ox, but in eating it; but he perceived by the lowing that it was near, and therefore appears to delight in the lowing; and similarly he does not delight because he sees 'a stag or a wild goat', but because he is going to make a meal of it.

This psychology of animals is entirely speculative; I personally think dogs seem to delight greatly in the scent of hares, even when the hare is long gone and there is no chance of eating one. I've known dogs who chased rabbits with great pleasure even if they wouldn't hurt it once they caught it, just because they loved to chase them.  

Temperance and self-indulgence, however, are concerned with the kind of pleasures that the other animals share in, which therefore appear slavish and brutish; these are touch and taste. But even of taste they appear to make little or no use; for the business of taste is the discriminating of flavours, which is done by winetasters and people who season dishes; but they hardly take pleasure in making these discriminations, or at least self-indulgent people do not, but in the actual enjoyment, which in all cases comes through touch, both in the case of food and in that of drink and in that of sexual intercourse. This is why a certain gourmand prayed that his throat might become longer than a crane's, implying that it was the contact that he took pleasure in.

So, food and drink and sex is what we're really interested in here. These do often tend to get people in trouble.  

Thus the sense with which self-indulgence is connected is the most widely shared of the senses; and self-indulgence would seem to be justly a matter of reproach, because it attaches to us not as men but as animals. To delight in such things, then, and to love them above all others, is brutish. For even of the pleasures of touch the most liberal have been eliminated, e.g. those produced in the gymnasium by rubbing and by the consequent heat; for the contact characteristic of the self-indulgent man does not affect the whole body but only certain parts.

We don't usually think of the self-indulgent as being especially inclined to the gymnasium, and Aristotle seems willing to grant that exception. I do think that there may be exceptions to this exception, however; but that is a topic for another time.