According to Ethical Response-Dependent Realism (ERDR), moral properties are response-dependent: for something to instantiate a moral property is for it to be disposed to elicit the right kind of response in the right kind of respondent. Most mornings I like ERDR. I like it mostly because it allows us to combine cognitivism and internalism. If a moral commitment is the cognizing of a disposition to elicit a motivational response in me, then both cognitivism and internalism are true of moral commitments.
Sadly, I just read a very interesting argument by Nick Zangwill against ERDR (in Erkenntnis 59: 285-290, 2003). The argument is that non-vacuous versions of ERDR are incompatible with the existence of action on the motive of duty. The argument is based on three ideas:
(DUTY) There is such a thing as acting on the motive of duty – doing the right thing for its own sake
(KNOWN) The essence of moral properties either is (or at least could be) known by us.
(TRY) If an agent A knows that E is the essence of properties P, then in trying to instantiate P, A tries to instantiate E.
Side note: Zangwill construes the “is” version of KNOWN as a commitment of analytic ERDR, according to which the response-dependence is part of the very concept of a moral property, and the “could be” version as a commitment of synthetic ERDR, according to which the response-dependence is the unobvious underlying nature of a moral property.
Zangwill’s argument can be formulated as a reductio. Assume for reductio that ERDR is true. The conjunction of ERDR and KNOWN entails the following:
1) Moral properties’ being dispositions to elicit the right responses in the right respondents either is (or at least could be) known by us.
The conjunction of 1 and TRY entails:
2) In trying to instantiate moral properties, we try to instantiate a disposition to elicit the right responses in the right respondents (or at least would upon discovering that moral properties are response-dependent).
However, acting on the motive of duty just means that one acts with disregard for the responses one’s action might elicit. That is, DUTY entails this:
3) We sometimes try to instantiate moral properties but do not try to instantiate any responses in any respondents (and would not try to instantiate any responses in any respondents upon discovering that moral properties are response-dependent).
It’s important to realize that giving up on 3 means giving up on the possibility of acting purely on the motive of duty.
The problem is that 2 entails the negation of 3:
4) We never try to instantiate moral properties without trying to instantiate any responses in any respondents (or at least would never so try upon discovering that moral properties are response-dependent).
Thus we reach an absurdity: the contradiction between 3 and 4.
I don’t know if there’s been discussion of this argument in the literature, but it seems pretty plausible on the face of it. The weakest links are probably those bridge principles that do not pertain to the meta-ethical substance of the argument, notably TRY. Suppose I try to buy gold. Is it true that I am thereby trying to buy atomic element 79? Perhaps the intensionality of trying is enough to secure that something like TRY is false. At any rate, that would be my first reaction in defending ERDR.