The Angelic Doctor Against the Errors of the Greeks - Chapter 23

How the assertion: the creature cannot cooperate with the Creator, is to be understood.

Perplexing also is what Athanasius says in his discourse on the Council of Nicaea: “Or let them tell us how the creature cooperates with the Creator.”  Thereby it is implied that the creature cannot cooperate with the Creator. This seems false, since the saints are said by the Apostle to be God’s helpers and fellow-workers.” (1 Cor. 3:9)

It must be borne in mind, however, that something is said to cooperate with another in two ways. First, because it works toward the same effect, but by a different power, as a servant cooperates with his lord, or an instrument with the artisan by whom it is moved. Second, something is said to cooperate with another in so far as it effects conjointly with another the same operation, as when two men carry a single burden or drag a boat.

A creature, therefore, can cooperate in the first way with the Creator in respect to effects which come to pass through the creature, but not in respect to those effects which are immediately from God such as creation and sanctification. A creature, however, does not cooperate in the second way with the Creator; only the three persons of the Trinity cooperate in this way, since theirs is a single operation: not, however, as if each possessed a part of the power by which the operation is performed as is the case with many men dragging a boat, for thus the power of each would be imperfect; but in the sense that the entire power sufficient for the effect is in each of the three Persons.