If the former, then what makes his commands good is that they are compatible with the particular nature that he has, and not merely because they are his commands. But then God is not needed as a basis for morality, since in this case what makes something moral is just that it conforms to what any being with that nature would want (whether such a being exists or not). And that is inconsistent with the MDCT.
If the latter, however, then his commands would still be good even if his nature were entirely different. And that means that if he did command torturing babies, it would be good to do so — and thus we have not avoided the problem that plagued the traditional Divine Command Theory.
Unsurprisingly, the above criticism has itself come under attack by proponents of the MDCT. Their attempts to fix the theory, however, reveal a deeper problem — namely, that they have two incompatible views as to what is essentially moral. Like almost everyone else, they believe that what's essentially moral are acts that are kind, fair, etc. Yet they also believe — or want very much to believe — that what's essentially moral is whatever God wants.
Some of them openly attempt to have it both ways. William Alston, for instance, claims that “God is good by virtue of being loving, just, merciful and so on” (i.e., he wouldn't be good otherwise) — but then says that these very things are good only “because they are features of God” (i.e., they wouldn't be good if there wasn't a God).* But that makes no sense.
We can perhaps more easily see that it doesn't by means of an analogy that Alston himself makes (though he of course draws a different conclusion from it):
The standard for the meter unit used to be a platinum bar kept at a constant temperature in Paris — just as the standard of goodness for divine command theorists is God. But now, if we think of the meter as being defined as the length of that bar (whatever it is at any given moment), it follows that if the bar expanded slightly, the meter would also become slightly longer. This corresponds to the view that good is defined as the will of God, so that if his will were different, what is good would be different as well. If, on the other hand, we think of the bar as being a meter because it is of a particular length, then if the bar expands slightly, it is no longer exactly a meter long. This corresponds to the view that God's will is good because he is a caring being, and would not be good if he weren't. But it's one or the other; one can't have it both ways. To claim that the bar is a meter long because it has that particular length, and that a meter just means the length of that bar (whatever it is), makes no sense. And that is what Alston is doing when it comes to morality.
Some proponents of the MDCT have attempted to escape the dilemma by claiming that God's properties are necessary. God could not be anything but the caring being that he is — and this, it is said, means that one cannot meaningfully consider what would be the case if he were different.
But even supposing God's properties could not be anything other than what they in fact are, it still remains the case that we don't necessarily know what they are. Therefore, it does make sense to ask what it would mean on this theory if God commanded something like torturing babies. To put it another way, we must distinguish between metaphysical and epistemic possibilities. It may be metaphysically impossible for God to command such a horrible thing, but we don't know that it is, and so must consider it as a possibility.
At this point, the proponent of the MDCT may reply that the theory is supposed to explain the metaphysical basis for morality; it isn't necessarily supposed to guarantee that we know what the correct morality is. We may not know what is or isn't possible for God to command, but the fact remains that there are certain things that it would be impossible for him to ask of us — and if in fact he is necessarily a caring being, he could not command horrible things like torturing babies.
But now the question one should ask is why the theist feels so confident that God's nature is that of a caring being. It can't be simply because he has revealed this to us, for he could be a being with the opposite characteristics who has so far been lying! Obviously, the reason theists think he is kind, fair, etc., is because they regard such things as good. But that just means they regard them as good independently of God having that nature. And that's incompatible with the MDCT.
The same thing applies if the proponent of the theory simply defines God as a caring being — so that if these weren't the creator's properties, the creator wouldn't be God. In that case, we could be certain that God wouldn't command horrible acts. But again, the question is, why define God this way unless it is because such properties are already regarded as good? The meter bar was selected as the standard in part because it was of the right length, the length of other measuring instruments that already existed to represent (albeit less precisely) meters. Similarly, God is thought of by divine command theorists to be the standard of goodness because he is thought to have a nature that is of the right type, a type that is independently regarded as good.
Proponents of the theory therefore should either admit that they accept independent moral principles, or else bite the bullet and say that morality depends on God's morally-arbitrary will, so that even torturing babies might turn out to be good. The MDCT does not solve the problems found in the traditional Divine Command Theory.
* William Alston, “What Euthyphro Should Have Said,” in William Lane Craig, ed., Philosophy of Religion: A Reader and Guide, p. 292.
[Originally published at Debunking Christianity]