This is the second post in a series of posts about the Moral Twin Earth.
In this paper Horgan and Timmons pose a dilemma for Copp and versions of moral naturalism where moral terms refer to some natural property. On the first horn, the reference-fixing relation R is too ambiguous to fix determinate natural properties and there are too many eligible natural properties that satisfy R. For example, maybe R satisfies both consequentialist and deontological theories. On the second horn, if the reference-fixing relation R is precise enough to fix a determinate natural property, a Moral Twin Earth scenario can be constructed such that what R fixes on Earth is different than what R fixes on Twin Earth. This leads to an objectionable relativism. Depending on the version of moral naturalism, they will be guilty of one of two types of objectionable relativism. If it turns out that moral terms between Earthlings and Twin Earthlings have different meanings and different referents, then it will be guilty of chauvinistic conceptual relativism. If it turns out that moral terms between Earthlings and Twin Earthlings have same meanings but different referents, then they it will be guilty of standard relativism–since what they both say in a genuine disagreement can be true.
Horgan and Timmons consider Copp’s first reply—the best translation reply—and say Copp’s reply is based on a misunderstanding: Copp mistakenly thought the MTE argument presupposes that sameness of meaning (between Earthling and Twin Earthling moral terms) requires sameness of referent. (This misunderstanding is probably due Horgan and Timmons criticizing Boyd’s semantics in constructing their original MTE.) In fact, the MTE argument also works against a semantic theory that have sameness of meaning but different referents. Boyd’s semantic account–where sameness of meaning entails sameness of referent–is guilty of chauvinistic conceptual relativism, while semantic accounts that have same meanings but different referents are guilty of standard relativism.
On Copp’s second reply, he argues that it will turn out–based on Putnam’s semantics–that the Earthlings and Twin Earthlings have sameness in meaning and referents, thereby avoiding criticisms of relativism. But Horgan and Timmons reply that Copp hasn’t actually filled in the details of the reference-fixing R relation; Copp has merely said that there will be sameness in meaning and referents without saying how it will be done. And, it could turn out that once this R relation is specified the referent is nonnatural (or supernatural), thus refuting naturalism.
And, finally, on what Copp says is the “major error” in the MTE argument; namely, the point that we need to take into account mistakes about beliefs, Horgan and Timmons reply that this has no bearing on the argument. What Horgan and Timmons want is Copp to produce a reference-fixing relation R that won’t be susceptible to the dilemma of either being too indeterminate, or determinate and leading to objectionable relativism.
In the next post, Copp accepts the challenge of constructing a determinate reference-fixing relation R.