Whether a man may merit anything from God?

Image: Detail from Triumph of St. Thomas Aquinas over Averroes by Benozzo Gozzoli (1420–97)

It is written (Jeremiah 31:16): “There is a reward for thy work.” Now a reward means something bestowed by reason of merit. Hence it would seem that a man may merit from God.

Merit and reward refer to the same, for a reward means something given anyone in return for work or toil, as a price for it. Hence, as it is an act of justice to give a just price for anything received from another, so also is it an act of justice to make a return for work or toil. Now justice is a kind of equality, as is clear from the Philosopher (Ethic. v, 3), and hence justice is simply between those that are simply equal; but where there is no absolute equality between them, neither is there absolute justice, but there may be a certain manner of justice, as when we speak of a father's or a master's right (Ethic. v, 6), as the Philosopher says. And hence where there is justice simply, there is the character of merit and reward simply. But where there is no simple right, but only relative, there is no character of merit simply, but only relatively, in so far as the character of justice is found there, since the child merits something from his father and the slave from his lord.

Now it is clear that between God and man there is the greatest inequality: for they are infinitely apart, and all man's good is from God. Hence there can be no justice of absolute equality between man and God, but only of a certain proportion, inasmuch as both operate after their own manner. Now the manner and measure of human virtue is in man from God. Hence man's merit with God only exists on the presupposition of the Divine ordination, so that man obtains from God, as a reward of his operation, what God gave him the power of operation for, even as natural things by their proper movements and operations obtain that to which they were ordained by God; differently, indeed, since the rational creature moves itself to act by its free-will, hence its action has the character of merit, which is not so in other creatures.

Thomas Aquinas, Summa Theologica (I-II Question 114, Article 1)