Reply to Objection 3: Although in this unhappy abode we participate, after a fashion, in the Divine good, by knowledge and love, yet the unhappiness of this life is an obstacle to a perfect participation in the Divine good: hence this very sorrow, whereby a man grieves for the delay of glory, is connected with the hindrance to a participation of the Divine good.
Whether the spiritual joy which proceeds from charity, can be filled?
Objection 1: It would seem that the spiritual joy which proceeds from charity cannot be filled. For the more we rejoice in God, the more is our joy in Him filled. But we can never rejoice in Him as much as it is meet that we should rejoice in God, since His goodness which is infinite, surpasses the creature's joy which is finite. Therefore joy in God can never be filled.
Objection 2: Further, that which is filled cannot be increased. But the joy, even of the blessed, can be increased, since one's joy is greater than another's. Therefore joy in God cannot be filled in a creature.
Objection 3: Further, comprehension seems to be nothing else than the fulness of knowledge. Now, just as the cognitive power of a creature is finite, so is its appetitive power. Since therefore God cannot be comprehended by any creature, it seems that no creature's joy in God can be filled.
On the contrary, Our Lord said to His disciples ( Jn. 15:11 ): "That My joy may be in you, and your joy may be filled."
I answer that, Fulness of joy can be understood in two ways; first, on the part of the thing rejoiced in, so that one rejoice in it as much as it is meet that one should rejoice in it, and thus God's joy alone in Himself is filled, because it is infinite; and this is condignly due to the infinite goodness of God: but the joy of any creature must needs be finite. Secondly, fulness of joy may be understood on the part of the one who rejoices. Now joy is compared to desire, as rest to movement, as stated above (FS, Q[25], AA[1],2), when we were treating of the passions: and rest is full when there is no more movement. Hence joy is full, when there remains nothing to be desired. But as long as we are in this world, the movement of desire does not cease in us, because it still remains possible for us to approach nearer to God by grace, as was shown above (Q[24], AA[4],7). When once, however, perfect happiness has been attained, nothing will remain to be desired, because then there will be full enjoyment of God, wherein man will obtain whatever he had desired, even with regard to other goods, according to Ps. 102:5 : "Who satisfieth thy desire with good things." Hence desire will be at rest, not only our desire for God, but all our desires: so that the joy of the blessed is full to perfection---indeed over-full, since they will obtain more than they were capable of desiring: for "neither hath it entered into the heart of man, what things God hath prepared for them that love Him" ( 1 Cor. 2:9 ). This is what is meant by the words of Lk. 6:38 : "Good measure and pressed down, and shaken together, and running over shall they give into your bosom." Yet, since no creature is capable of the joy condignly due to God, it follows that this perfectly full joy is not taken into man, but, on the contrary, man enters into it, according to Mat. 25:21 : "Enter into the joy of thy Lord."
Reply to Objection 1: This argument takes the fulness of joy in reference to the thing in which we rejoice.
Reply to Objection 2: When each one attains to happiness he will reach the term appointed to him by Divine predestination, and nothing further will remain to which he may tend, although by reaching that term, some will approach nearer to God than others. Hence each one's joy will be full with regard to himself, because his desire will be fully set at rest; yet one's joy will be greater than another's, on account of a fuller participation of the Divine happiness.
Reply to Objection 3: Comprehension denotes fulness of knowledge in respect of the thing known, so that it is known as much as it can be. There is however a fulness of knowledge in respect of the knower, just as we have said of joy. Wherefore the Apostle says ( Col. 1:9 ): "That you may be filled with the knowledge of His will, in all wisdom and spiritual understanding."
Whether joy is a virtue?
Objection 1: It would seem that joy is a virtue. For vice is contrary to virtue. Now sorrow is set down as a vice, as in the case of sloth and envy. Therefore joy also should be accounted a virtue.
Objection 2: Further, as love and hope are passions, the object of which is "good," so also is joy. Now love and hope are reckoned to be virtues. Therefore joy also should be reckoned a virtue.
Objection 3: Further, the precepts of the Law are about acts of virtue. But we are commanded to rejoice in the Lord, according to Phil. 4:4 : "Rejoice in the Lord always." Therefore joy is a virtue.
On the contrary, It is not numbered among the theological virtues, nor among the moral, nor among the intellectual virtues, as is evident from what has been said above (FS, QQ[57],60,62).
I answer that, As stated above (FS, Q[55], AA[2],4), virtue is an operative habit, wherefore by its very nature it has an inclination to a certain act. Now it may happen that from the same habit there proceed several ordinate and homogeneous acts, each of which follows from another. And since the subsequent acts do not proceed from the virtuous habit except through the preceding act, hence it is that the virtue is defined and named in reference to that preceding act, although those other acts also proceed from the virtue. Now it is evident from what we have said about the passions (FS, Q[25], AA[2],4) that love is the first affection of the appetitive power, and that desire and joy follow from it. Hence the same virtuous habit inclines us to love and desire the beloved good, and to rejoice in it. But in as much as love is the first of these acts, that virtue takes its name, not from joy, nor from desire, but from love, and is called charity. Hence joy is not a virtue distinct from charity, but an act, or effect, of charity: for which reason it is numbered among the Fruits ( Gal. 5:22 ).
Reply to Objection 1: The sorrow which is a vice is caused by inordinate self-love, and this is not a special vice, but a general source of the vices, as stated above (FS, Q[77], A[4]); so that it was necessary to account certain particular sorrows as special vices, because they do not arise from a special, but from a general vice. On the other hand love of God is accounted a special virtue, namely charity, to which joy must be referred, as its proper act, as stated above (here and A[2]).
Reply to Objection 2: Hope proceeds from love even as joy does, but hope adds, on the part of the object, a special character, viz. "difficult," and "possible to obtain"; for which reason it is accounted a special virtue. On the other hand joy does not add to love any special aspect, that might cause a special virtue.
Reply to Objection 3: The Law prescribes joy, as being an act of charity, albeit not its first act.