William Lane Craig and Massimo Pigliucci debated the existence of God in 1998. (Click here to read the transcript.) In his opening statement, Craig presented his standard moral argument for God’s existence.

(1) If God does not exist, objective moral values do not exist.

(2) Objective values do exist.

(3) Therefore, God exists.

In his opening statement, Pigliucci denied (2).

Finally, the problem of morality, which I’m sure we’ll have more to say about–oh yeah, I agree with Dr. Craig when he cited Dr. Ruse, a philosopher of science. There is no such a thing as objective morality. We got that straightened out.

Although this was much too quick to constitute anything much like an effective debate rebuttal, this quotation is useful for another reason. It reveals that Pigliucci agrees with Michael Ruse’s argument against (2). Regular readers of this blog will remember that Ruse’s argument for error theory has been the subject of much criticism by philosophers (see here and the references provided; cf. the links here), but Pigliucci says nothing in the debate which would answer or pre-empt those objections. In fairness to Pigliucci, some or all of those criticisms were published after the debate. The point here is not that Pigliucci should be faulted for failing to refute objections before they are published. Rather, the point is that he (apparently) relied upon a fallacious argument to justify his denial of (2).

He continues:

Morality in human cultures has evolved and is still evolving, and what is moral for you might not be moral for the guy next door and certainly is not moral for the guy across the ocean, the Atlantic or the Pacific Ocean, and so on. And what makes you think that your personal morality is the one and everybody else is wrong? Now a better way of putting this is that it is not the same as to say that anything goes; it is not at all the same. What goes is anything that works; there are things that work. Morality has to work. For example, one of the very good reasons we don’t go around killing each other is because otherwise the entire society as we know it would collapse and we’d become a bunch of simple isolated animals. There are animals like those.

I, for one, find that statement to be so  vague as to be of little philosophical value. What, precisely, does Pigliucci mean when he says, “Morality in human cultures has evolved?” And what does that have to do with the branch of metaethics known as moral ontology, the actual focus of Craig’s moral argument? One possible answer is that Pigliucci is simply making the point that human beliefs–about moral goodness and badness; moral obligation, permittedness, and prohibition; and the like–have changed over time. If that is what Pigliucci meant, then perhaps his point was that changes in human moral beliefs over time is further evidence against (2).

But if that is the sort of argument Pigliucci had in mind, it’s hard to see how it could be successful. Consider the following argument.

(4) Human beliefs about the laws of physics have changed over time.

(5) The best explanation for these changes in human beliefs is that there are no objective truths about the laws of physics.

(6) Therefore, there are no objective truths about the laws of physics.

I think probably everyone would agree that this argument fails because (5) is false. Now consider the parallel argument from changes in moral beliefs over time.

(7) Human beliefs about morality have changed over time.

(8) The best explanation for these changes in human beliefs is that there are no objective truths about morality.

(9) Therefore, there are no objective truths about morality.

It’s far from obvious why the moral beliefs argument is any better than the physics belief argument.

In Pigliucci’s First Rebuttal, he said this:

Let’s go back to this thing of objective morality. I think that there’s a little bit of twisting and turning around here with terms. Again, it’s not a matter of “Is there out there an objective morality?” We know that there isn’t. There are some components of your own morality that are not shared by other human beings. So either you are pretentious enough to think that your morality for whatever reason is the only correct one, or everybody else in the world is wrong.

I think that that is pretentious. ….

In this passage, Pigliucci seems to be stating a version of the argument from moral disagreement. But, as it stands, this argument is multiply flawed. First, Pigliucci conflates “the existence of ontologically objective moral values” with “my [the speaker’s] moral beliefs are the only correct moral beliefs.” The former neither entails nor makes probable the latter; this argument is a non sequitur. Second, Pigliucci fails to consider rival explanations to error theory, such as “the fact that much moral disagreement is due to disagreement about non-ethical facts” and “moral disagreement is much more surprising on the conjunction of theism and moral objectivism than on moral objectivism and metaphysical naturalism.”

Moving on, Pigliucci next makes a comparison between the behavior of human beings and other animals.

Of course there are some universals that all human beings share. Just today, for example, I told my students in a biology class that there are some things that human beings and society would never approve because of the way human societies are built. One, of course, is homicide; another one, of course, is rape. However, what we call homicide or rape or, in fact, even infanticide is very, very common among different types of animals. Lions, for example, commit infanticide on a regular basis because they want to make sure that the little offspring that is being raised by the lioness is their own and not someone else’s. Now, are these kinds of acts to be condoned? I don’t even know what that means because the lion doesn’t understand what morality is, that’s for sure.

It’s not entirely clear to me what point Pigliucci is trying to make in this passage. Perhaps his idea is that human “universals,” such as the beliefs that homicide and rape are morally wrong, aren’t evidence for an “objective morality” because those same behaviors are common in other animals. Again, it’s far from clear how such an argument would work. Here are two objections. First, humans are moral agents whereas lions are not. (Note: the previous sentence should not be interpreted as implying that humans possess libertarian free will.) Second, even if there were such a thing as ‘lion morality,’ it’s far from obvious why facts about ‘lion morality’ have any relevance to or bearing upon human morality. If Pigliucci has an argument, he hasn’t yet told us what it is.

Morality is an invention of human beings. It’s a very good invention. I’m not suggesting we should abandon morality. I’m not suggesting, more to the point, that we should abandon ethics. Ethics is a perfectly valid way of thinking about things. We can all agree as a society that there are things that are wrong and things that are good. We can act on them, and we can enforce those things, but there is no higher power or no higher reason to tell us that this is right or this is wrong. Unfortunately, we are on our own; that’s my humble opinion. I would really like for somebody to come down from the sky and tell me what is right and what is wrong. My life would be much, much easier. Unfortunately, that doesn’t happen.

The key claim in this paragraph is its first sentence: “Morality is an invention of human beings.” There’s no argument presented for that claim, however.

Finally, it’s worth noticing the reasons Pigliucci gives to deny the existence of objective moral values and obligations. He doesn’t claim, “Objective moral values and duties can exist only if God exists, but God doesn’t exist; therefore, objective moral values and duties don’t exist.” Rather, Pigliucci gives independent reasons for rejecting moral objectivism, i.e., reasons that are independent of his atheism. The upshot is this: although Pigliucci denies the existence of objective moral values and obligations, atheism does not entail the non-existence of objective moral values and obligations.