Reply Obj. 3: The intellect apprehends the end before the will does: yet motion towards the end begins in the will. And therefore to the will belongs that which last of all follows the attainment of the end, viz. delight or enjoyment.
Reply Obj. 4: Love ranks above knowledge in moving, but knowledge precedes love in attaining: for "naught is loved save what is known," as Augustine says (De Trin. x, 1). Consequently we first attain an intelligible end by an act of the intellect; just as we first attain a sensible end by an act of sense.
Reply Obj. 5: He who has whatever he desires, is happy, because he has what he desires: and this indeed is by something other than the act of his will. But to desire nothing amiss is needed for happiness, as a necessary disposition thereto. And a good will is reckoned among the good things which make a man happy, forasmuch as it is an inclination of the will: just as a movement is reduced to the genus of its terminus, for instance, "alteration" to the genus "quality." ________________________
FIFTH ARTICLE [I-II, Q. 3, Art. 5]
Whether Happiness Is an Operation of the Speculative, or of the
Practical Intellect?
Objection 1: It would seem that happiness is an operation of the practical intellect. For the end of every creature consists in becoming like God. But man is like God, by his practical intellect, which is the cause of things understood, rather than by his speculative intellect, which derives its knowledge from things. Therefore man's happiness consists in an operation of the practical intellect rather than of the speculative.
Obj. 2: Further, happiness is man's perfect good. But the practical intellect is ordained to the good rather than the speculative intellect, which is ordained to the true. Hence we are said to be good, in reference to the perfection of the practical intellect, but not in reference to the perfection of the speculative intellect, according to which we are said to be knowing or understanding. Therefore man's happiness consists in an act of the practical intellect rather than of the speculative.
Obj. 3: Further, happiness is a good of man himself. But the speculative intellect is more concerned with things outside man; whereas the practical intellect is concerned with things belonging to man himself, viz. his operations and passions. Therefore man's happiness consists in an operation of the practical intellect rather than of the speculative.
On the contrary, Augustine says (De Trin. i, 8) that "contemplation is promised us, as being the goal of all our actions, and the everlasting perfection of our joys."
I answer that, Happiness consists in an operation of the speculative rather than of the practical intellect. This is evident for three reasons. First because if man's happiness is an operation, it must needs be man's highest operation. Now man's highest operation is that of his highest power in respect of its highest object: and his highest power is the intellect, whose highest object is the Divine Good, which is the object, not of the practical but of the speculative intellect. Consequently happiness consists principally in such an operation, viz. in the contemplation of Divine things. And since that "seems to be each man's self, which is best in him," according to Ethic. ix, 8, and x, 7, therefore such an operation is most proper to man and most delightful to him.