, but not every science is.
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FOURTH ARTICLE [I-II, Q. 34, Art. 4]

Whether Pleasure Is the Measure or Rule by Which to Judge of Moral
Good or Evil?

Objection 1: It would seem that pleasure is not the measure or rule
of moral good and evil. Because "that which is first in a genus is
the measure of all the rest" (Metaph. x, 1). But pleasure is not the
first thing in the moral genus, for it is preceded by love and
desire. Therefore it is not the rule of goodness and malice in moral
matters.

Obj. 2: Further, a measure or rule should be uniform; hence that
movement which is the most uniform, is the measure and rule of all
movements (Metaph. x, 1). But pleasures are various and multiform:
since some of them are good, and some evil. Therefore pleasure is not
the measure and rule of morals.

Obj. 3: Further, judgment of the effect from its cause is more
certain than judgment of cause from effect. Now goodness or malice of
operation is the cause of goodness or malice of pleasure: because
"those pleasures are good which result from good operations, and
those are evil which arise from evil operations," as stated in
_Ethic._ x, 5. Therefore pleasures are not the rule and measure of
moral goodness and malice.

_On the contrary,_ Augustine, commenting on Ps. 7:10 "The searcher of
hearts and reins is God," says: "The end of care and thought is the
pleasure which each one aims at achieving." And the Philosopher says
(Ethic. vii, 11) that "pleasure is the architect," i.e. the
principal, "end [*St. Thomas took _finis_ as being the nominative,
whereas it is the genitive--_tou telous_; and the Greek reads "He"
(i.e. the political philosopher), "is the architect of the end."], in
regard to which, we say absolutely that this is evil, and that, good."

_I answer that,_ Moral goodness or malice depends chiefly on the
will, as stated above (Q. 20, A. 1); and it is chiefly from the end
that we discern whether the will is good or evil. Now the end is
taken to be that in which the will reposes: and the repose of the
will and of every appetite in the good is pleasure. And therefore man
is reckoned to be good or bad chiefly according to the pleasure of
the human will; since that man is good and virtuous, who takes
pleasure in the works of virtue; and that man evil, who takes
pleasure in evil works.

On the other hand, pleasures of the sensitive appetite are not the
rule of moral goodness and malice; since food