In the context of his defense of the metaethical argument, William Lane Craig considers some examples of aliens from the Andromeda galaxy who come to Earth and attack, either raping and killing humans, or eating humans. I will raise some objections to Craig’s metaethical argument based on that.
Now, the Andromeda galaxy is perhaps too far away even for advanced aliens, so let’s say that aliens who evolved on another planet in the Milky Way come to Earth. Rape is very improbable in that scenario (why would they want to rape humans in the first place?), and eating humans is also very improbable (why not a more efficient way of getting food, even if humans happened to be edible to them?), but let’s say that they want to eat humans for whatever reason.
Moreover, let’s say that the aliens evolved differently, and they have a sense more or less similar to our sense of right and wrong in the way it feels to them, but associated with different behaviors and/or situations, entities, etc. – which is at least compatible with Craig’s scenario, and in fact seems to be what the scenario is about.
Speaking of those scenarios (or the Andromeda variant, galaxy of origin is irrelevant to the matter at hand), Craig claims:
I think this extraterrestrial illustration is a very powerful illustration that, in the absence of God, human morality isn’t objective. It has no more claim to be objective than some extraterrestrial alien morality.
Let’s say that the aliens in question also have a different visual system. We can see that some of the aliens are green, and some are red. But they do not perceive any such differences. However, they do perceive some differences that look to them similar to our perception of different colors in a number of cases in which we perceive no chromatic differences.
So, one might mirror Craig’s argument and make a metachromatic argument for theism:
I think this extraterrestrial illustration is a very powerful illustration that, in the absence of God, human color isn’t objective. It has no more claim to be objective than some extraterrestrial alien color.
But that clearly does not work.
In fact, even if God exists, the aliens might have different visual systems. Also, it seems clear that regardless of whether aliens have different visual systems, if the aliens were to claim, in English, that they are all the same color, they would be making a false claim, whereas our claim that some are red and some green would remain true.
However, Craig has not shown that morality is relevantly different from color in this case. Why would aliens with different visual perceptions (say, color*, or alien color?) would be no threat to the objectivity of color (or rather, color statements to be precise, but let’s leave that aside to simplify), but would be a threat in the case of morality?
That’s one difficulty for Craig’s argument. Another one is the following one:
Is Craig implicitly making a wide-ranging claim about exobiology?
More precisely, is Craig implying that no aliens with something more or less similar to our moral sense in the way it feels to them, but associated with different behaviors, states, entities, etc., exist, anywhere in the whole universe? Is he further implying that no such aliens are nomologically possible? How about metaphysically possible?
If Craig is not making the implication that there actually are no such aliens, then there is the following problem:
Craig’s metaethical theory is that a creature’s moral obligations are God’s commands.
So, if aliens like that do exist, given that God created them (by means of evolution) without a moral sense that yields a negative assessment of a potential action on their part consisting of invading the Earth and eating humans, then it seems plausible that God did not command them not to invade the Earth and eat humans. But then, it would not be immoral for said aliens to invade the Earth and eat humans.
So, even if God exists, and going by Craig’s own metaethical theory, it seems that we humans have no moral claim against such aliens if they exist. But if so, in particular, it seems that the conclusion that those aliens who evolved differently would not be doing anything morally wrong if they invaded the Earth and ate humans does not entail or suggest that morality is not objective.
However, in that case, let’s assume that God does not exist for the sake of the argument, and the aliens in question attack and eat humans. There are two possibilities:
a. The aliens’ actions are immoral, even if they do not have a moral sense that lets them realize that. That would be akin to the fact that some of the aliens are green and others red, even if they do not have a visual sense that perceives that difference.
b. The aliens’ actions are not immoral.
Either way, there appears to be no threat to moral objectivity in the sense of ‘objective’ relevant to Craig’s metaethical argument, which blocks Craig’s argumentation.
In fact, as long as Craig is not implying that aliens with such different minds do not in fact exist, Craig’s own position seems to entail that if theism is true and aliens with that kind of mind attack and eat humans, their actions are not immoral. So, if the non-immorality of the aliens’ actions would not be a problem for moral objectivity on theism, why would it be a problem for moral objectivity on non-theism?
Granted, someone might say that theism entails moral objectivity. But my point here is that from an assumption that the aliens’ actions are not immoral, it does not follow that morality is not objective.
An alternative would be for Craig to claim that there actually are no aliens that have something more or less akin to a moral sense but associated with different behaviors, situations, etc. But in that would be a wide-ranging claim about exobiology. Is Craig actually implying that? If so, I think he ought to clarify it.
Even if he made that claim, there would be other problems related to this matter – apart of course from the problem of justifying such a claim.
One of those problems is the one I mentioned above, namely the color parallel: that in order to argue for the objectivity of morality, Craig gives the example that the Holocaust was immoral regardless of whether anyone believes. However, it’s also true that Nazi uniforms were not red regardless of whether anyone believes.
So, it seems that the same argument for objective morality works for objective color. So, color is objective. But what if there are aliens with different visual systems, like the ones outlined above?
Unless Craig is committed to a wide-ranging claim about exobiology with regard to alien visual systems, it seems to me he ought to explain why the existence of aliens with visual systems like those outlined above would not be a problem for color objectivity, yet aliens with something somewhat similar to our moral system but different in the sense outlined above would be a problem for moral objectivity. What’s the difference? (i.e., the difference that is relevant with regard to objectivity, in the sense of the term ‘objective’ used in the context of Craig’s metaethical argument).
 Arguably a claim that there actually are no such aliens would not suffice, since one might consider possible even if not actual scenarios. But it seems to me that there is no need to argue that point in this context, since denying actuality is already a wide-ranging claim about exobiology.