Thomas Aquinas in the Summa Theologica addresses the question of human happiness in the Treatise on Human Happiness. Parts of the definitions he provides or systematic explanations contained therein can perhaps appear at first to be counter-intuitive when seen through the worldly fashion of “common” sense. For instance, Aquinas is uncompromising on the notion of perfect happiness necessitating the Last End of human existence, namely, God. God, for Aquinas, is an uncreated perfection that cannot be fully possessed short of the perfection of the human person in Heaven. Therefore, Aquinas reasons that no created good can satisfy the desire for ultimate fulfillment. Only the perfect Creator can grace the human creature with the perfect happiness that Aquinas en-visions in the Summa (I-II, q. 5. a. 3).
Aquinas reasons, by examining the nature of the world in which he lives, that the perfection of human happiness is not in this life. By way of deduction he concludes that perfect happiness can therefore only potentially lie in the hereafter, that is, dependent on the just desserts of Heaven or Hell or Purgatory. For Aquinas, suffering or the inherent imperfections of human nature (sin) as well as the natural imperfections of lesser created “goods” will be replaced with the ultimate satisfaction of “the Good” itself through, with or in, God in Heaven. Aquinas concludes in the Treatise on Human Happiness that the perfection of human fulfillment is the uncreated God who is not or cannot be satisfactorily had in earthly existence (I-II, q. 5 a. 1).
Aquinas spells out in the Treatise his position with regard to the various rival goods of life. He hierarchically orders created goods from the least fulfilling goods to those that in this life begin to approximate the eternal perfection of human happiness in Heaven. Goods that Aquinas lists in the Treatise on Human Happiness include the following: wealth, honors, fame or glory, power, bodily goods (health), pleasure (carnal), goods of the soul (virtue), or created goods in general (immanent human flourishing). Each is dealt with in turn, then relegated to the realm of imperfect goods by way of identifying faults that leave the good ultimately imperfectly satisfying for the human person (I-II, q. 2 a. 1-8). Aquinas deduces with what is essentially a “process of elimination” that perfect happiness is nothing other than God. There is no perfect happiness with God here, so perfect happiness is in Heaven.
Tension arises in Aquinas' account with regard to the prominence of the Last End of human happiness being placed in an altogether different category from immanent human flourishing. A prudent question with regard to Aquinas' position on human happiness is whether he is right to finalize imperfect happiness relative to his overriding concern with absolute fulfillment that is not here, but with God in an essentially different mode of existence in Heaven. God in Heaven is the sole means by which the human person is made perfectly fulfilled. However, that Heaven is “perfect” happiness via the uncreated “Good” that is God means that Aquinas' vision of the afterlife is contingent on the uncreated grace of God being inaccessible to the finite human person in this world in the same manner that Aquinas imagines happiness in Heaven to be perfect (I-II, q. 3. a. 1).
Labeling imperfect the happiness of immanent human flourishing, or the excellence of virtue, or the enjoyment of created goods, is contingent on whether Aquinas is right about the essence of Heaven's qualitative distinction from the known world with regard to happiness. What Aquinas calls imperfect goods can be aspects of the perfect Good when the perfect Good is present in this life in the same way here that it is in Heaven via the uncreated grace that Aquinas believes distinguishes Heaven. Aquinas is often interpreted to understand created goods of imperfect earthly happiness in terms of created graces that perfect the imperfections of human nature (I-II q. 112 a. 1). For Aquinas, human nature exists apart from the grace that God creates, while the grace that God creates is not God Himself in essence (which is reserved for the perfection of Heaven) but rather another mode of participation in the created world that remains fundamentally imperfect without the Final End.
Division into perfect or imperfect happiness in Aquinas is highly speculative. There is admittedly no intrinsic error with speculative philosophy, especially regarding the Scholastic project. Nevertheless, tension does arise when a fundamental part of Aquinas' Treatise on Happiness is contestable or problematic. For example, Aquinas holds that final or perfect happiness is “nothing else” than the vision of the divine essence (I-II q. 3. a. 8). That perfect happiness is rare albeit possible in this life is denied by Aquinas based on the conclusion that human nature cannot see or have the divine essence. The divine essence is the uncreated grace that for Aquinas is God's perfection unencumbered by the imperfections of the finite creation.
One can test Aquinas' position by the same means of deduction by which the conclusion that perfect happiness is only in Heaven is reached. In other words, using Aquinas' own criteria of judgment, the ideal of perfection being possible in this life can be examined when the field of happiness is narrowed to essential imperfections that Aquinas believes cannot be surpassed without first altering the world into another realm that permits perfect human happiness. The list of imperfect goods is worth summarizing to demonstrate the point.
First, Aquinas discounts wealth for being an instrumental means to other ends. Hoarding money is essentially dissatisfying when considered apart from usage (I-II q. 2. a. 1). Moreover, Aquinas eliminates honors, fame or glory, for being contingent on the opinions of others in much the same way. Favor from others is relatively desirable but cannot fulfill the person in the ultimate manner that Aquinas means (I-II q. 2. a. 2-3). Likewise, power is rejected for having no intrinsic perfection beyond the uses toward which the power is used. Similar to money, power is satisfying or dis-satisfying relative to what you do with power or the honor you receive from having power (I-II q. 2 a. 4). Health (bodily good) is necessary for happiness in the same vein that ideal bodily perfection is necessary for happiness. No health means an imperfect physical body with which to perform virtue or enjoy goods (I-II q. 2 a. 5). Moreover, bodily pleasure is the instantiation of this or that good, not “the Good” in and of itself. An instantiation of pleasure is transient by definition not ultimately fulfilling (I-II q. 2 a. 6).
Virtue or the “good of the soul” is the habit of human excellence. For Aquinas virtue is almost ultimate fulfillment, but falls short for being an essentially instrumental perfection for the achievement of some other created good. However, virtue unlike the other imperfect instrumental goods can have every created good or the perfection of happiness in Heaven for an object. Hence, virtue is one of the highest goods for Aquinas (I-II q. 2 a. 7). Finally, Aquinas questions whether any created good whatsoever can provide the perfect happiness that he sees missing from the above. His answer is no (I-II q. 2 a. 8). Created goods cannot be the source of their own perfections but rather only an imperfect part or transient aspect of an uncreated (immutable) transcendent Good, meaning the essence God Himself. The Summum Bonum is God. God is the Summum Bonum. Perfect happiness is in seeing the divine essence or in being perfected by the divine essence by seeing the vision of the divine essence (according to Aquinas' understanding of the divine). Perfect happiness is nowhere but in Heaven. That that is so is the key question that is being addressed.
Aquinas can be challenged on the above when his notion of Heavenly perfection is considered more closely. For example, created goods (imperfect aspects of perfect satisfaction) can be perfectly maintained for the duration of terrestrial existence or even into the afterlife. Whether the person knows this or not during the course of his or her life is not the matter. For Aquinas, when death comes or Heaven is reached the attainment of earthly perfection is not lost, but finalized. Ultimate finalization in no way necessitates that perfect happiness is not possible while living in an imperfect world. Perfect satisfaction of every desire can be potentially fulfilled in this life with the possible exception of the desire for God Himself. Absence of the Final End causes Aquinas to disallow perfect happiness short of Heaven. Still, the desire for Heaven can be satisfied in this life by perfect faith. The certainty of Heaven can be attained by perfect grace.
Now, an objection to Aquinas on this vital issue is that there is nothing in the constitution of God's creation that eliminates the potential for perfect happiness amidst imperfect happiness. Aquinas' metaphysical notion of the vision of the divine essence in Heaven differs from the way in which the divine essence can be potentially en-visioned here. Aquinas believes that perfect happiness is not possible when there is an unsatisfied immanent or “transcendent” desire. An assumption is made by Aquinas that desire causes unhappiness so that there can be no desire or will in Heaven. Furthermore, Aquinas states that the observance of God's effects leads the person to desire to know the cause of the effects, who can be known only insofar that He exists, but not in essence. Still, God reveals his essence by way of revelation which is then known or seen with the eyes of faith. The essence of God's goodness, truth or beauty, is known by finite creatures with finite measure here as well as in Heaven.
There is no reason that Aquinas can absolutely reject either by faith or reason the notion that human persons who remain finite creatures in everlasting Heaven will continue to know God in essentially the same way that God is known here. Faith can know God here without doubt provided God's grace. Finite knowing ceases to be finite knowing in one way when the finite creature can know eternally. However, eternal finite knowing in no way necessitates some other means of knowing other than to continue to know the way finite human persons know now without end. Therefore, the same can be said of human happiness when the potential for human happiness is not limited by Aquinas' understanding of what necessitates an “imperfect” happiness in this life relative to the perfect happiness of Heaven. Namely, perfect happiness is possible in this life when the following conditions have been met: 1) there is no privation of imperfect goods 2) Heaven is known by faith 3) Heaven is attained by grace prior to death 4) God's uncreated grace (his essence) is already present in the same way that He will be present eternally in Heaven.