Objection 1. It would seem that every pleasure is evil. For that which destroys prudence and hinders the use of reason, seems to be evil in itself: since man's good is to be "in accord with reason," as Dionysius says (Div. Nom. iv). But pleasure destroys prudence and hinders the use of reason; and so much the more, as the pleasure is greater: wherefore "in sexual pleasures," which are the greatest of all, "it is impossible to understand anything," as stated in Ethic. vii, 11. Moreover, Jerome says in his commentary on Matthew [Origen, Hom. vi in Num.] that "at the time of conjugal intercourse, the presence of the Holy Ghost is not vouchsafed, even if it be a prophet that fulfils the conjugal duty." Therefore pleasure is evil in itself; and consequently every pleasure is evil.
Objection 2. Further, that which the virtuous man shuns, and the man lacking in virtue seeks, seems to be evil in itself, and should be avoided; because, as stated in Ethic. x, 5 "the virtuous man is a kind of measure and rule of human actions"; and the Apostle says (1 Corinthians 2:15): "The spiritual man judgeth all things." But children and dumb animals, in whom there is no virtue, seek pleasure: whereas the man who is master of himself does not. Therefore pleasures are evil in themselves and should be avoided.
Objection 3. Further, "virtue and art are concerned about the difficult and the good" (Ethic. ii, 3). But no art is ordained to pleasure. Therefore pleasure is not something good.
On the contrary, It is written (Psalm 36:4): "Delight in the Lord." Since, therefore, Divine authority leads to no evil, it seems that not every pleasure is evil.
I answer that, As stated in Ethic. x, 2,. some have maintained that all pleasure is evil. The reason seems to have been that they took account only of sensible and bodily pleasures which are more manifest; since, also in other respects, the ancient philosophers did not discriminate between the intelligible and the sensible, nor between intellect and sense (De Anima iii, 3). And they held that all bodily pleasures should be reckoned as bad, and thus that man, being prone to immoderate pleasures, arrives at the mean of virtue by abstaining from pleasure. But they were wrong in holding this opinion. Because, since none can live without some sensible and bodily pleasure, if they who teach that all pleasures are evil, are found in the act of taking pleasure; men will be more inclined to pleasure by following the example of their works instead of listening to the doctrine of their words: since, in human actions and passions, wherein experience is of great weight, example moves more than words.
We must therefore say that some pleasures are good, and that some are evil. For pleasure is a repose of the appetitive power in some loved good, and resulting from some operation; wherefore we assign a twofold reason for this assertion. The first is in respect of the good in which a man reposes with pleasure. For good and evil in the moral order depend on agreement or disagreement with reason, as stated above (Question 18, Article 5): just as in the order of nature, a thing is said to be natural, if it agrees with nature, and unnatural, if it disagrees. Accordingly, just as in the natural order there is a certain natural repose, whereby a thing rests in that which agrees with its nature, for instance, when a heavy body rests down below; and again an unnatural repose, whereby a thing rests in that which disagrees with its nature, as when a heavy body rests up aloft: so, in the moral order, there is a good pleasure, whereby the higher or lower appetite rests in that which is in accord with reason; and an evil pleasure, whereby the appetite rests in that which is discordant from reason and the law of God.
The second reason can be found by considering the actions, some of which are good, some evil. Now pleasures which are conjoined to actions are more akin to those actions, than desires, which precede them in point of time. Wherefore, since the desires of good actions are good, and of evil actions, evil; much more are the pleasures of good actions good, and those of evil actions evil.
Reply to Objection 1. As stated above (Question 33, Article 3), it is not the pleasures which result from an act of reason, that hinder the reason or destroy prudence, but extraneous pleasures, such as the pleasures of the body. These indeed hinder the use of reason, as stated above (Question 33, Article 3), either by contrariety of the appetite that rests in something repugnant to reason, which makes the pleasure morally bad; or by fettering the reason: thus in conjugal intercourse, though the pleasure be in accord with reason, yet it hinders the use of reason, on account of the accompanying bodily change. But in this case the pleasure is not morally evil; as neither is sleep, whereby the reason is fettered, morally evil, if it be taken according to reason: for reason itself demands that the use of reason be interrupted at times. We must add, however, that although this fettering of the reason through the pleasure of conjugal intercourse has no moral malice, since it is neither a mortal nor a venial sin; yet it proceeds from a kind of moral malice, namely, from the sin of our first parent; because, as stated in the I, 98, 2 the case was different in the state of innocence.
Reply to Objection 2. The temperate man does not shun all pleasures, but those that are immoderate, and contrary to reason. The fact that children and dumb animals seek pleasures, does not prove that all pleasures are evil: because they have from God their natural appetite, which is moved to that which is naturally suitable to them.
Reply to Objection 3. Art is not concerned with all kinds of good, but with the making of external things, as we shall state further on (57, 3). But actions and passions, which are within us, are more the concern of prudence and virtue than of art. Nevertheless there is an art of making pleasure, namely, "the art of cookery and the art of making arguments," as stated in Ethic. vii, 12.
Source: Summa Theologica (New Advent)