If both powers are said to exert the same kind of independent creative efficacy, an objection about two creators of one event arises. But divine creation and human voluntary acquisition describe different attributions.
The claim that “one act cannot be under two powers” is therefore ambiguous unless “under” is explained. Under one respect the act is created; under another it is voluntarily acquired by a human.
Distinguishing creation from acquisition clarifies how comprehensive divine power is discussed alongside human responsibility.