210 days until the first class . . . .
As I have gone through the readings for Philosophy 5100 - Contemporary Moral Theory - I have expressed my problems with the discussion of the relevance of evolutionary theory to moral realism. I simply do not think that the concepts of "realism" and "anti-realism" are particularly clear.
After mentally struggling with this through the weekend, I came up with another way of asking the question which, I hope, would make the answer clearer.
That question is:
What does evolutionary theory debunk?
I think it is less confusing to suggest that what evolutionary theory actually debunks are external reasons. In other words, it vindicates Bernard Williams' thesis:
A has a reason to φ if and only if A has some desire the satisfaction of which will be served by his φ-ing. (Williams, B., 1979. “Internal and External Reasons,” reprinted in Moral Luck, Cambridge: Cambridge University Press, 1981, 101–13)
I think that Sharon Street's argument (Sharon Street, "A Darwinian Dilemma for Realist Theories of Value," Philosophical Studies 127 (2006): 109-66.) is actually a Darwinian dilemma for the external reasons thesis. The argument basically boils down to the claim that we do not need to postulate the existence of external reasons to explain any aspect of intentional action.
Evolutionary theory shows that much of what philosophers have attributed to external reasons (because they do not directly benefit the agent) can actually be explained in terms of evolved internal reasons. Because external reasons have no role to play in the explanation of real world events, we have reason to treat them like unicorns, ghosts, and gremlins. They might exist independent of our ability to detect them, but we have no reason to believe that they do.
There seems to be some dispute as to whether this is a metaphysical claim (external reasons do not exist) or an epistemological claim (external reasons might exist but we have no reason to believe that they do) - but this question is just as applicable to unicorns, ghosts, and gremlins.
(NOTE: There are those who claim that we must also postulate an irresistible illusion that there are external reasons - e.g., Michael Ruse, "Morality is a collective illusion foisted upon us by our genes." However, this "illusion" might be like the illusion that the sun goes around the earth. It is not so much an illusion foisted upon us by our genes as a misinterpretation of what we perceive.)
There is one sense in which external reasons do exist. In the same way that all of the fingers that I have is a small portion of all of the fingers that exist, it is also the case that the (internal) reasons that I have is a subset of all of the internal reasons that exist. Other beings exist, and they also have their own (internal) reasons to act in particular ways.
There is reason to believe that evolution has created in each of us - to varying degrees - internal reasons to act in ways that benefit others. For example, evolution has given parents internal reasons to care for their offspring. We do not need to postulate any type of external reason to explain why parents do this.
The fact that another person has a reason to avoid being in a state of pain does not imply that I have a reason to avoid creating a state in which that person is in a state of pain. For me to have an reason to avoid putting that person in such a state, I have to have a desire that would be served by avoiding the realization of such a state.
However, the fact that the other person has an aversion to being in a state of pain does imply that he has a reason to cause me to avoid actions that would put her in a state of pain, and to perform actions that would prevent her from being in a state of pain. She can do this in two ways.
She can reward me for acting in ways that make it less likely that she will be in pain, or threaten to punish me if I should act in ways that put her in a state of pain. In other words, she can link my φ-ing to serving the desires that I have in such a way that what serves my existing desires is that which makes it less likely that she will be in a state of pain.
In addition, she can attempt to alter my desires so that the actions that serve those desires are those that make it less likely that she will be in a state of pain. She has a reason to cause me to have aversions to actions that would tend to result in her being in pain, such as (most directly) an aversion to causing pain for others. She can do this, for example, by praising those who refrain from actions that put others in pain or perform actions that reduce the chance that others will experience pain, and by condemning those who act in ways that tend to result in others being in pain.
What evolutionary theory actually debunks, then, is the hypothesis that there are external reasons that are independent of all internal reasons. What impact this has on moral realism depends on one's views of morality and realism. If one equates moral realism with external-reasons realism, then evolutionary theory creates a problem for moral realism. If, on the other hand, one is comfortable with the idea that internal reasons are real, and that the internal reasons one has is a subset of internal reasons that exist, we may have moral realism without external-reasons realism.