Just as human beings acquire the first thing that completes them, i.e., the soul, from the action of God, so they also acquire the last thing that completes them, that is complete human happiness, directly from God, and they rest in him. This is clear from the fact that the natural longing of a human being cannot rest in anything else except in God alone. For human beings have an innate longing that moves them from the things that have been brought into being to seeking their cause. Therefore this longing will not rest until it reaches the first cause, which is God.
[Thomas Aquinas, Disputed Questions on the Virtues, Atkins and Williams, eds. Cambridge UP (New York: 2005) p. 65.]