Does God answer prayer according to the prayer’s reality or merely according to a knowledge of the prayer? Suppose on an A theory of time, that God knows future contingencies, which are not yet real, by some means (perhaps scientia visionis, though I’m not sure how – maybe even this knowledge would have to be by middle knowledge on A theory). Supposing that he knows that at some future time t1 Tommy prays for his friend Billy, who at time t1 has already passed away. God, at time t0, when Billy is still alive, knows that “Tommy will pray for Billy at t1” with deductive closure. However, since Tommy’s prayer is not yet in any sense ‘real’, does God answer the prayer, or rather does he simply act according to his knowledge of the prayer? If the prayer at t1 is efficacious for Billy then God, it seems, must not answer prayer, but rather simply act according to his knowledge of prayers. Therefore, on A theory, God does not answer certain prayers which Christian theology classically presumes him to.
This is another good argument, from what is common currency in Christian theology, to reject the A theory of time advocated by people such as William Lane Craig.