I answer that, While some of the Stoics maintained that all pleasures are evil, the Epicureans held that pleasure is good in itself, and that consequently all pleasures are good. They seem to have thus erred through not discriminating between that which is good simply, and that which is good in respect of a particular individual. That which is good simply, is good in itself. Now that which is not good in itself, may be good in respect of some individual in two ways. In one way, because it is suitable to him by reason of a disposition in which he is now, which disposition, however, is not natural: thus it is sometimes good for a leper to eat things that are poisonous, which are not suitable simply to the human temperament. In another way, through something unsuitable being esteemed suitable. And since pleasure is the repose of the appetite in some good, if the appetite reposes in that which is good simply, the pleasure will be pleasure simply, and good simply. But if a man's appetite repose in that which is good, not simply, but in respect of that particular man, then his pleasure will not be pleasure simply, but a pleasure to him; neither will it be good simply, but in a certain respect, or an apparent good.
Reply Obj. 1: The virtuous and the useful depend on accordance with reason, and consequently nothing is virtuous or useful, without being good. But the pleasant depends on agreement with the appetite, which tends sometimes to that which is discordant from reason. Consequently not every object of pleasure is good in the moral order which depends on the order of reason.
Reply Obj. 2: The reason why pleasure is not sought for the sake of something else is because it is repose in the end. Now the end may be either good or evil; although nothing can be an end except in so far as it is good in respect of such and such a man: and so too with regard to pleasure.
Reply Obj. 3: All things seek pleasure in the same way as they seek good: since pleasure is the repose of the appetite in good. But, just as it happens that not every good which is desired, is of itself and verily good; so not every pleasure is of itself and verily good. ________________________
THIRD ARTICLE [I-II, Q. 34, Art. 3]
Whether Any Pleasure Is the Greatest Good?
Objection 1: It would seem that no pleasure is the greatest good. Because nothing generated is the greatest good: since generation cannot be the last end. But pleasure is a consequence of generation: for the fact that a thing takes pleasure is due to its being established in its own nature, as stated above (Q. 31, A. 1). Therefore no pleasure is the greatest good.
Obj. 2: Further, that which is the greatest good cannot be made better by addition. But pleasure is made better by addition; since pleasure together with virtue is better than pleasure without virtue. Therefore pleasure is not the greatest good.
Obj. 3: Further, that which is the greatest good is universally good, as being good of itself: since that which is such of itself is prior to and greater than that which is such accidentally. But pleasure is not universally good, as stated above (A. 2). Therefore pleasure is not the greatest good.
On the contrary, Happiness is the greatest good: since it is the end of man's life. But Happiness is not without pleasure: for it is written (Ps. 15:11): "Thou shalt fill me with joy with Thy countenance; at Thy right hand are delights even to the end."