Thomas relies heavily on Aristotle, Cicero, and Seneca in his discussion of gratitude, but at one crucial point he introduces a distinctively Christian theme. Must we thank everyone who does us a beneficium ? Thomas answers with 1 Thessalonians 5:18: In all things give thanks.
Ultimately, since God is cause of all things, thanks is due for all things and in all circumstances to God. But that means that benefactors serve God’s purposes, and that in turn means that the recipient should respond to a benefactor with a gratitude that matches “their relationship.”
Seneca said something similar, but Paul enables Thomas to affirm global gratitude more fully than Seneca. It is difficult for Seneca to make sense of thanking someone who does a favor only for his own benefit. A Christian, however, can see God’s causal hand in the benefit, overriding the wrong motives of the benefactor. Because of his gratitude to God, the Christian is more apt to see the good in the benefit rather than the evil of the motivation.