Many maintain that petitionary prayer is pointless. I argue that the theist can defend petitionary prayer by giving a general account of how divine and creaturely causation can be compatible and complementary, based on the claim that the goodness of something depends on its cause. I use Thomas Aquinas’s metaphysical framework to give an account that explains why a world with creaturely causation better reflects God’s goodness than a world in which God brought all things about immediately. In such a (...) world, prayer could allow us to cause good things in a distinctive way: by asking God for them. (shrink)