Abstract
In this article, I seek to assess the extent to which Theism, the claim that there is a God, can provide a true fundamental explanation for the existence of the infinite plurality of concrete and abstract possible worlds, posited by David K. Lewis and Alvin Plantinga. This assessment will be carried out within the (modified) explanatory framework of Richard Swinburne, which will lead to the conclusion that the existence of God provides a true fundamental explanation for these specific entities. And thus, given the truth of this type of explanation, we have another good abductive argument for God’s existence and grounds for affirming a weaker form of the principle of methodological naturalism in our metaphysical theorising.