Heaven.

St. Thomas Aquinas (1225-74) wrote two large Summas, the Summa Theologica (Sum of Theology) and the Summa Contra Gentiles (Summa against non-Catholics). Aquinas was a Dominican, and this latter work was written at the request of Dominican missionaries who were dialoguing with Jews and Moslems in Toledo, Spain. Its first three books are purely philosophical; the fourth and last book deals also with revelation.

By the time Aquinas came to deal with divine providence in book three, he had already established philosophically the existence and attributes of God and the immortality of the human soul. It remained for him to deal with the goal of human life. He agreed with Aristotle that the highest faculty of the human being is the intellect (along with intellectual desire, which we call the will) and that therefore the goal of life is knowledge and the happiness which comes from it. He agreed with Aristotle also that each being has as its goal to be as much like God (for Aristotle, the gods) as is possible to its nature. Since God is providential, he gives each creature powers proper to its nature. Now, human beings automatically, necessarily, desire happiness. They also desire lasting happiness, indeed eternal happiness. As well, they desire perfect happiness, infinite happiness. Humans therefore are made for God; otherwise God would have made them contradictory beings, that is, beings with desires that they must have but which cannot be fulfilled.

Natural happiness for man would then consist in the highest knowledge of God possible to him and the maximum grasp attainable by him of the highest good, God. As far as philosophy could be sure, for those who had lived good lives this would be an exalted knowledge of God and a proportional happiness resulting from it.

Humans, however, revelation tells us, are not made for a merely natural happiness. They are called to live with the life of God himself and share his knowledge and his happiness. This is a tremendously higher goal. We are made to see God face to face! It is clear however that our supernatural goal is not separated from our natural goal. It's the fulfillment of it; it's based on it, and it enables us to possess what is given to us only by the free decision of God over and above our natural power. It completes our natural power by fulfilling it and going beyond it in the same direction.

There is a big problem how to account for the fact that those who get to heaven always remain there. Plato said that those who arrived in his Platonic heaven returned, after a long time, to earth, to earn their way to heaven again. Why is that not the case with the heaven of revelation? The answer is that angels and saints in heaven share not only in God's knowledge and his happiness but also in his freedom. In heaven we are perfectly free; on earth our freedom is imperfect. Here on earth we can sin; in heaven we cannot sin. The reason is that in heaven our intellect and will are necessitated. There is one object which we cling to necessarily once we attain it. Aquinas explains that, when we see God face to face, God who is infinite being, infinite truth, infinite beauty, we are so captivated that nothing else can draw us away; we cannot choose anything in preference to God. That's the kind of freedom God himself has. He can't sin because no creature can tempt him to do so.

Freedom which includes freedom to sin is an imperfect freedom. Freedom which is not subject to sin is perfect freedom. Even in this life the saints approximate somewhat to that freedom. Their love of God is so great that most things don't tempt them, though of course their freedom is not yet fully perfect.

We can thus see that, though by our nature we have a high, eternal calling, nevertheless by our supernature, by our living with the life of God himself, we are called to a higher, eternal calling, one which renders us incapable of sinning, incapable of losing the Beatific Vision and the tremendous happiness that flows from it.