I'd like to comment on Stephen Law's "Evil God Challenge." There's a YouTube version of this in his debate with William Lane Craig. The gist of his argument, as I construe it, is that since the world contains both good and evil, the evidence doesn't select for a good Creator rather than an evil Creator. Explanations to account for why a good Creator allows evil can be mirrored by explanations to account for why an evil Creator allows good. In addition, you can invoke inscrutability for the designs of an evil God just as you can invoke inscrutability for the designs of a good God, thus mimicking skeptical theism.
i) Even if the argument was successful, it would be an argument for agnosticism, not atheism. It would create a stalemate between prima facie evidence for a benevolent God's existence and prima facie evidence for a malevolent God's existence.
ii) Isn't Law's challenge just a variation on the Cartesian demon? Even if we can't disprove it, so what? Why should we take that any more seriously than other ingenious, but fanciful thought-experiments? Humans have the ability to concoct imaginary intellectual traps. Even if we can't escape from imaginary traps of our own devising, there's no reason to think it's true. It's just cleverness. Indeed, Law himself considers his thought-experiment to be absurd. So what is there to disprove?
iii) And if it were true, isn't there something incoherent about fretting over the possibility of a global delusion? I mean, if there really were a global delusion, how would we even be cognizant of that spectral possibility? How would we have the objectivity to step outside the delusion in order to consider it from an outsider's perspective?
Isn't the point of Cartesian demon hypothetical to raise doubts about what we think we know or can prove? But that's paradoxical, for if the Cartesian demon actually existed, we'd be incapable of resisting the delusive beliefs he implants in us. So there's something incoherent about the hypothetical. The Cartesian demon won't allow us to doubt the global illusion. Won't allow us to suspect his sinister designs, behind-the-scenes.
And Law's thought-experiment seems to be a weaker version of the Cartesian demon. But if the argument fails in the greater case, then a fortiori, will it not fail in the lesser case?
iv) If it's legit for atheists like Law to play the Evil God card, why can't Christians play the Last Thursdayism card when atheists appeal to empirical evidence for evolution or global warming–or the "oppression" of homosexuals in church history? When you exercise the nuclear option in philosophy (i.e. global skepticism), you're stuck with Mutually Assured Destruction.
v) Another problem is whether evil is strictly the opposite of good. One doesn't have to buy into the whole privative theory of evil to appreciate that evil is parasitic on good. So the notion that if there can be a maximally good being, there can be a maximally evil being is not self-evident. He needs to show how good and evil can truly mirror each other. For Law's argument to get off the ground, he must take the preliminary step of showing that good and evil are relevantly symmetrical, so that you can have "maximal" representatives of each. But if evil is parasitic on good, then the comparison is equivocal.