Objection 1. It would seem that external goods also are necessary for Happiness. For that which is promised the saints for reward, belongs to Happiness. But external goods are promised the saints; for instance, food and drink, wealth and a kingdom: for it is said (Luke 22:30): "That you may eat and drink at My table in My kingdom": and (Matthew 6:20): "Lay up to yourselves treasures in heaven": and (Matthew 25:34): "Come, ye blessed of My Father, possess you the kingdom." Therefore external goods are necessary for Happiness.
Objection 2. Further, according to Boethius (De Consol. iii): happiness is "a state made perfect by the aggregate of all good things." But some of man's goods are external, although they be of least account, as Augustine says (De Lib. Arb. ii, 19). Therefore they too are necessary for Happiness.
Objection 3. Further, Our Lord said (Matthew 5:12): "Your reward is very great in heaven." But to be in heaven implies being in a place. Therefore at least external place is necessary for Happiness.
On the contrary, It is written (Psalm 72:25): "For what have I in heaven? and besides Thee what do I desire upon earth?" As though to say: "I desire nothing but this,"--"It is good for me to adhere to my God." Therefore nothing further external is necessary for Happiness.
I answer that, For imperfect happiness, such as can be had in this life, external goods are necessary, not as belonging to the essence of happiness, but by serving as instruments to happiness, which consists in an operation of virtue, as stated in Ethic. i, 13. For man needs in this life, the necessaries of the body, both for the operation of contemplative virtue, and for the operation of active virtue, for which latter he needs also many other things by means of which to perform its operations.
On the other hand, such goods as these are nowise necessary for perfect Happiness, which consists in seeing God. The reason of this is that all suchlike external goods are requisite either for the support of the animal body; or for certain operations which belong to human life, which we perform by means of the animal body: whereas that perfect Happiness which consists in seeing God, will be either in the soul separated from the body, or in the soul united to the body then no longer animal but spiritual. Consequently these external goods are nowise necessary for that Happiness, since they are ordained to the animal life. And since, in this life, the felicity of contemplation, as being more Godlike, approaches nearer than that of action to the likeness of that perfect Happiness, therefore it stands in less need of these goods of the body as stated in Ethic. x, 8.
Reply to Objection 1. All those material promises contained in Holy Scripture, are to be understood metaphorically, inasmuch as Scripture is wont to express spiritual things under the form of things corporeal, in order "that from things we know, we may rise to the desire of things unknown," as Gregory says (Hom. xi in Evang.). Thus food and drink signify the delight of Happiness; wealth, the sufficiency of God for man; the kingdom, the lifting up of man to union of God.
Reply to Objection 2. These goods that serve for the animal life, are incompatible with that spiritual life wherein perfect Happiness consists. Nevertheless in that Happiness there will be the aggregate of all good things, because whatever good there be in these things, we shall possess it all in the Supreme Fount of goodness.
Reply to Objection 3. According to Augustine (De Serm. Dom. in Monte i, 5), it is not material heaven that is described as the reward of the saints, but a heaven raised on the height of spiritual goods. Nevertheless a bodily place, viz. the empyrean heaven, will be appointed to the Blessed, not as a need of Happiness, but by reason of a certain fitness and adornment.
Source: Summa Theologica (New Advent)