Stephen Law’s argument concerning Evil God was very interesting. Within the Internet discussion that followed some suggested this argument lends itself to a parallel moral argument. It goes like this:
1. If Evil God does not exist, then objective moral values do not exist.
2. Objective moral values do exist.
3. Therefore, Evil God exists.
Now, at first glance, one may be tempted to say that the first premise is false, since we believe the Christian God (who is all-good) exists. Hence, it is the case that Evil God does not exist, and yet objective moral values do exist. However, as an objection to the argument it qualifies as question-begging. Hence, we must find another way to critique the premise(s) if we are to avoid the conclusion.
(1) seems to rely on just the same sort of reasoning we use to justify (1*) (the premise of the original moral argument for God– “If God does not exist, then objective moral values do not exist”). That is to say, plausibly, objective moral values can only originate from a person. Well, Evil God is a person. The atheist or Good God Skeptic (GGS) here contends there is just as much explanatory power in Evil God or God, and therefore we should remain, at best, agnostic about both (1) and (1*).
I do not think this succeeds either. A number of considerations need to be explained here. First, it is somewhat controversial whether or not evil is actually a “thing” in relation to good. Evil just seems to be a privation of the good. The GGS may here simply state that it is the other way around on an Evil God-account of objective morality. This leads us to our second consideration. Most people perceive objective moral duties as obligations to do good. Note what this is not saying: this does not claim that what people perceive they ought to do is always objectively good. Rather, it is the mere fact that they perceive what they ought to do (regardless of what that actually is) is actually good. This is an incredibly powerful observation when one thinks about it.
The third observation logically proceeds from the second. It seems to be a truth inherent to moral duties (which are derived from moral values) that whenever one performs an act in accordance with an objective moral duty he has done what is good. That is, it seems if it is the case that one ought to do X, then one’s doing of X is in fact good, and not evil! Perhaps here the GGS will retort that rather than being good and evil, the real delineation for objective moral duties is “right” and “wrong,” and thus the axiom above should be read: “if it is the case that one ought to do X, then one’s doing of X is in fact right, and not wrong.” Fair enough. This leads to:
Fourthly, related to the previous point, is that it makes no sense to speak of duty-fulfillment in terms of moral objectivity as “right” and yet objectively evil. This is what I mean. Suppose the being who grounds morality commands Jackie to do some act A. She happily agrees to do A, since she typically desires to do what the being commands. At this point, A constitutes an obligation. Jackie’s fulfillment of A is right and if she were to reject or fail to fulfill A it would be wrong. Now if this moral being were to be all-evil, then her fulfillment of A, though right, would be itself evil! This seems horrendously confused and violates normal sensibilities.
Finally, if Evil God existed, this would make good a privation of evil. That is to say, good very plausibly is just the lack of committing evil. But since evil is usually described in terms of failing to do good, or doing the opposite of good, or whatnot, and good cannot be explained on this account except as a failure to do evil or privation of evil, it seems the Evil God account of objective morality fails after all. At the very least, it is less plausible than an all-good account of objective morality, given what morality is and our moral intuitions.
And that is the central point. The key distinguishing feature with respect to morality is that Evil God just is less plausible, all things being equal, than an all-good God, if morality is to be explained by one of them. Even if we decide to grant both beings the same level of explanatory scope and power (the latter of which is dubious), the Evil God hypothesis is a far more complex (and thus gratuitous) explanation, and without compelling evidence is not to be preferred over the good God hypothesis.
So we can see, on moral considerations and intuitions alone, that good God is untainted, and Evil God remains implausible, even for the GGS.
 It is helpful here to note this kind of “inference to the best explanation” is only in regards to the competing first premises of the respective arguments, (1) and (1*), and not to the arguments themselves, which are deductive.
 Some may point to the ontological argument and the idea of maximal greatness to show God is to be preferred over Evil God. This is, I think, quite correct. However, I wanted to vindicate the moral argument as typically presented by the Christian in favor of God.