According to Stephen Law's "evil-god challenge," the hypothesis that there exists an omnipotent, omniscient, and maximally good creator of the universe (henceforth, theism) is no more plausible than the hypothesis that there exists an omnipotent, omniscient, and maximally evil creator of the universe (henceforth, maltheism). In defense of this contention, Law argues that theism and maltheism are a priori approximately equally plausible (call this claim prior symmetry) and that the available evidence (especially the evidence regarding the distribution of good and evil in the world) does not favor one hypothesis over the other (call this evidential symmetry). From here, Law claims that (rightly) no one takes maltheism seriously. It is surely a very implausible hypothesis. But given prior symmetry and evidential symmetry (which jointly entail what Law calls the symmetry thesis, according to which theism and maltheism are approximately equally reasonable), it follows that the same holds true of theism. Thus, theism is a very implausible hypothesis that should be rejected.
