On the contrary, Our Lord said ( Jn. 17:3 ): "This is eternal life: that they may know Thee, the only true God." Now eternal life is the last end, as stated above (A[2], ad 1). Therefore man's happiness consists in the knowledge of God, which is an act of the intellect.
I answer that, As stated above (Q[2], A[6]) two things are needed for happiness: one, which is the essence of happiness: the other, that is, as it were, its proper accident, i.e. the delight connected with it. I say, then, that as to the very essence of happiness, it is impossible for it to consist in an act of the will. For it is evident from what has been said (AA[1],2; Q[2], A[7]) that happiness is the attainment of the last end. But the attainment of the end does not consist in the very act of the will. For the will is directed to the end, both absent, when it desires it; and present, when it is delighted by resting therein. Now it is evident that the desire itself of the end is not the attainment of the end, but is a movement towards the end: while delight comes to the will from the end being present; and not conversely, is a thing made present, by the fact that the will delights in it. Therefore, that the end be present to him who desires it, must be due to something else than an act of the will.
This is evidently the case in regard to sensible ends. For if the acquisition of money were through an act of the will, the covetous man would have it from the very moment that he wished for it. But at the moment it is far from him; and he attains it, by grasping it in his hand, or in some like manner; and then he delights in the money got. And so it is with an intelligible end. For at first we desire to attain an intelligible end; we attain it, through its being made present to us by an act of the intellect; and then the delighted will rests in the end when attained.
So, therefore, the essence of happiness consists in an act of the intellect: but the delight that results from happiness pertains to the will. In this sense Augustine says (Confess. x, 23) that happiness is "joy in truth," because, to wit, joy itself is the consummation of happiness.
Reply to Objection 1: Peace pertains to man's last end, not as though it were the very essence of happiness; but because it is antecedent and consequent thereto: antecedent, in so far as all those things are removed which disturb and hinder man in attaining the last end: consequent inasmuch as when man has attained his last end, he remains at peace, his desire being at rest.
Reply to Objection 2: The will's first object is not its act: just as neither is the first object of the sight, vision, but a visible thing. Wherefore, from the very fact that happiness belongs to the will, as the will's first object, it follows that it does not belong to it as its act.
Reply to Objection 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 to Objection 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 to Objection 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."
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.
Objection 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.
Objection 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.
Secondly, it is evident from the fact that contemplation is sought principally for its own sake. But the act of the practical intellect is not sought for its own sake but for the sake of action: and these very actions are ordained to some end. Consequently it is evident that the last end cannot consist in the active life, which pertains to the practical intellect.
Thirdly, it is again evident, from the fact that in the contemplative life man has something in common with things above him, viz. with God and the angels, to whom he is made like by happiness. But in things pertaining to the active life, other animals also have something in common with man, although imperfectly.
Therefore the last and perfect happiness, which we await in the life to come, consists entirely in contemplation. But imperfect happiness, such as can be had here, consists first and principally, in an operation of the practical intellect directing human actions and passions, as stated in Ethic. x, 7,8.
Reply to Objection 1: The asserted likeness of the practical intellect to God is one of proportion; that is to say, by reason of its standing in relation to what it knows, as God does to what He knows. But the likeness of the speculative intellect to God is one of union and "information"; which is a much greater likeness. And yet it may be answered that, in regard to the principal thing known, which is His Essence, God has not practical but merely speculative knowledge.
Reply to Objection 2: The practical intellect is ordained to good which is outside of it: but the speculative intellect has good within it, viz. the contemplation of truth. And if this good be perfect, the whole man is perfected and made good thereby: such a good the practical intellect has not; but it directs man thereto.
Reply to Objection 3: This argument would hold, if man himself were his own last end; for then the consideration and direction of his actions and passions would be his happiness. But since man's last end is something outside of him, to wit, God, to Whom we reach out by an operation of the speculative intellect; therefore, man's happiness consists in an operation of the speculative intellect rather than of the practical intellect.
Whether happiness consists in the consideration of speculative sciences?
Objection 1: It would seem that man's happiness consists in the consideration of speculative sciences. For the Philosopher says (Ethic. i, 13) that "happiness is an operation according to perfect virtue." And in distinguishing the virtues, he gives no more than three speculative virtues---"knowledge," "wisdom" and "understanding," which all belong to the consideration of speculative sciences. Therefore man's final happiness consists in the consideration of speculative sciences.
Objection 2: Further, that which all desire for its own sake, seems to be man's final happiness. Now such is the consideration of speculative sciences; because, as stated in Metaph. i, 1, "all men naturally desire to know"; and, a little farther on (2), it is stated that speculative sciences are sought for their own sakes. Therefore happiness consists in the consideration of speculative sciences.
Objection 3: Further, happiness is man's final perfection. Now everything is perfected, according as it is reduced from potentiality to act. But the human intellect is reduced to act by the consideration of speculative sciences. Therefore it seems that in the consideration of these sciences, man's final happiness consists.