Peter van Inwagen proposes a criterion of philosophical success. He takes it to support an extremely pessimistic view about philosophy. He thinks that all philosophical arguments for substantive conclusions fail, including the argument from evil. I’m more optimistic on both counts. I’ll identify problems with van Inwagen’s criterion and propose an alternative. I’ll then explore the differing implications of our criteria. On my view, philosophical arguments can succeed and the argument from evil isn’t obviously a failure.