Michael Ruse is a philosopher of biology and an atheist who is well-known for his writings about evolution. In various writings, Ruse has argued against moral realism by appealing to (Darwinian) evolution. Instead, he argues, the scientific facts about evolution justify the conclusion that moral error theory is correct. In this post, I want to assess Ruse’s argument against moral realism and for error theory.
In his 1989 book, The Darwinian Paradigm, Michael Ruse argues that evolution, specifically Darwinian evolution, shows that morality cannot have an objective foundation.
The position of the modern evolutionist, therefore, is that humans have an awareness of morality – a sense of right and wrong and a feeling of obligation to be thus governed because such an awareness is of biological worth. Morality is a biological adaptation no less than are hands and feet and teeth (Mackie 1978, Murphy 1982, Ruse and Wilson 1985).
One premise of the argument, then, seems to be:
(1) Morality is a biological adaptation.
Let’s continue. Ruse writes:
Darwinian theory does speak to foundations, albeit in a negative sense. My claim is that the recognition of morality as merely a biological adaptation shows that there can be no foundation of the kind traditionally sought, whether by evolutionists, Christians or others!
The statement, “the recognition of morality as merely a biological adaptation shows that there can be no foundation of the kind traditionally sought,” suggests that another premise for Ruse’s argument is:
(2) If morality is a biological adaptation, then it cannot have an objective foundation.
And from there the implicit conclusion seems to be:
(3) Therefore, morality cannot have an objective foundation.
Why does Ruse think that morality cannot have an objective foundation if it is nothing but a biological adaptation? Ruse asks us to perform the following a thought experiment.
Start with the fact that the argument about the train goes through because and only because the existence of the train is assumed independently. Suppose, for instance, one had two worlds identical except that one has a speeding train and the other does not. There would be no reason to think the evolutionist is committed to a belief in speeding trains in both worlds. One is aware of the speeding train only because there is such a train. Now consider two worlds, one of which has an objective morality, whatever that might mean (God’s will? Nonnatural properties?), and the other world has no such morality. If the evolutionist’s case is well taken, the people in both worlds are going to have identical beliefs-subject to normal laws of causation and so forth. The existence of the objective ethics is in no way necessary for a derivation of our belief in an objective ethics from an evolutionary perspective. So, at the very least, what we can say is that an objective ethics is redundant to the evolutionist’s case.
Elsewhere, he writes:
The objectivist must agree that his / her ultimate principles are . . . redundant. You would believe what you do about right or wrong, irrespective of whether or not a ‘true’ right or wrong existed . . . Given two worlds, identical except that one has an objective morality and the other does not, the humans therein would think and act exactly the same ways, Hence the objective foundation for morality is redundant.
This passage suggests the following supporting argument for (2).
(4) On the assumption that evolution is true, an objective morality is not necessary to explain why people believe there is an objective morality.
(5) But the only reason we could have for believing in an objective morality is that they form part of the explanation for why we have the moral beliefs we do.
(6) Therefore, there is no reason to believe in an objective morality.
Let’s assume, but only for the sake of argument, that Ruse’s supporting argument is sound. How does Ruse justify the inference from (6) to (2)? As Lillehammer points out,
So far, however, Ruse has only made an epistemological claim about knowledge, not a metaphysical claim about truth. It does not follow from the fact that your belief that P varies regardless of whether or not P is true either that P is not true or that there is no fact about whether P is true.
In other words, Ruse at least seems to be confusing moral epistemology (the order of knowing) with moral ontology (the order of being). But is he?
As Lillehammer rightly points out, in order to evaluate Ruse’s argument, we have to understand what Ruse means by “objective” and “objectivity.” Before we consider what Ruse has written, let’s first distinguish between ontological and epistemological interpretations of objectivity. Morality is ontologically objective just in case some moral claims are true in virtue of corresponding to actually existing objects or properties that function as truthmakers for the claims in question. For example, someone who holds that morality is ontologically objective might maintain that the sentence “murder is wrong” is true because there is a real property, wrongness, and all moral acts that result in murder have that property. Moreover, all murders would have this property even if no one contemplated the moral status of murder and even if everyone thought that murder did not have such a property.
Moral values are epistemologically objective just in case some moral claims are such that they would be believed by (all?) impartial or rational persons who considered them; the claims in question need not have an objective ontological foundation. An epistemologically objective moral truth might have no ontological foundation at all, an objective ontological foundation (i.e., if it corresponded to natural or non-natural properties), or an intersubjective ontological foundation (i.e., if it corresponded to the moral beliefs of a group of people).
With this distinction in mind, let’s return to Ruse. As Lillehammer notes, in order to properly understood Ruse’s argument, we need to understand how Ruse defines his terms. It is odd, then, that Lillehammer doesn’t quote any passages from Ruse’s writings which clarify what Ruse has in mind. Fortunately for us, however, such passages are not hard to find. Here’s one.
Clearly, here, the evolutionist and the Christian part company. Admittedly, there is no unanimity among Christians as to the true foundations of morality. While some subscribe to a divine command theory, others (no doubt impressed by arguments which go back to Plato’s Euthyphro) would argue that there are independent standards of right and wrong to which even God subscribes. But, be this as it may, the Christian is surely committed to an independent, objective, moral code – a code which, ultimately, is unchanging and not dependent on the contingencies of human nature. (Of course, like any moralist, the Christian appreciates that different times and different places call for different applications of this code.)
The statement, “independent, objective, moral code — a code which, ultimately, is unchanging and not dependent on the contingencies of human nature,” suggests that Ruse has ontological objectivity in mind when he refers to objectivity. So we can reformulate his supporting argument as follows.
(4′) On the assumption that evolution is true, an ontologically objective morality is not necessary to explain why people believe there is an ontologically objective morality.
(5′) But the only reason we could have for believing in an ontologically objective morality is that the existence of an ontologically objective morality forms part of the explanation for why we have the moral beliefs we do.
(6′) Therefore, there is no reason to believe in an ontologically objective morality.
While Ruse at least defends (4′), he says nothing about (5′), perhaps because he thinks its truth is obvious. But its truth is not obvious to this writer. Many philosophers, including Richard Swinburne, have argued that moral truths are analytic truths. On the assumption that moral truths are analytic truths, then (5′) would be false. As Swinburne explains,
For the existence of the phenomena described by analytic truths needs no explanation. It does not need explaining that all bachelors are unmarried, or that if you add two to two you get four. These things hold inevitably and necessarily, whether or not there is a God.
Why does Ruse not consider the possibility that at least some objective moral truths are analytic? Because he rules out that in advance. Ruse can conclude that “the only reason we could have for believing in an ontologically objective morality is the actual existence of an ontologically objective morality” only by assuming there are no analytic truths about morality (and hence by assuming there are no ontologically objective moral truths). But Ruse asserts that the supporting argument is also supposed to lead to the intermediate conclusion that there are is no reason to believe in an ontologically objective morality, which in turn is supposed to lead to the ultimate conclusion that there is no ontologically objective morality. Thus, the thesis that there are no analytic truths about morality is both an assumption and an implication of the conclusion of his supporting argument. In other words, his supporting argument begs the question against ontologically objective morality.
 Michael Ruse, “Evolutionary Theory and Christian Ethics,” in The Darwinian Paradigm (London: Routledge, 1989), pp. 262, 268-269.
 Ruse 1989, 286.
 Michael Ruse, Taking Darwin Seriously (Oxford: Basil Blackwell, 1986), 254, as quoted in Hallvard Lillehammer, “Debunking Morality: Evolutionary Naturalism and Moral Error Theory” Biology and Philosophy 18 (2003): 567-581 at 576.
 Lillehammer 2003, 576.
 Lillehammer 2003, 577.
 Larry Arnhart, Darwinian Natural Right: The Biological Ethics of Human Nature (Albany: State University of New York Press, 1998).
 Geoffrey Sayre-McCord, “Introduction: The Many Moral Realisms” Essays on Moral Realism (ed. Geoffrey Sayre-McCord, Ithaca: Cornell University Press, 1988), 15.
 Ruse 1989, 269. Italics mine.
 Richard Swinburne, The Existence of God (revised ed., New York: Oxford University Press, 1991), 176.