In a recent paper, Dennis Whitcomb argues that omniscience is impossible. But if there cannot be any omniscient beings, then God, at least as traditionally conceived, does not exist. The objection is, roughly, that the thesis that there is an omniscient being, in conjunction with some principles about grounding, such as its transitivity and irreflexivity, entails a contradiction. Since each of these principles is highly plausible, divine omniscience has to go. In this article, I argue that Whitcomb's argument, if sound, has several unacceptable consequences. Among others, it implies that nobody knows that someone has knowledge, that, for most of us, all of our beliefs are false, and that there are no truths. This reductio all by itself provides sufficient reason to reject the argument. However, I also provide a diagnosis of where precisely the argument goes wrong. I argue that Whitcomb's crucial notion of grounding actually covers two distinct relations and that the principle of transitivity is true only for cases in which one of these relations holds rather than both of them. © 2012 Cambridge University Press.