ABSTRACT
This chapter contains a very brief introduction to moral twin earth, followed by a thought experiment. It is followed by a short discussion and then a series of questions. Richard Boyd thinks that he can establish that moral properties are identical to sets of natural properties by empirical means, rather than reflecting on the meanings of moral terms. For Boyd, moral terms are rigid designators, they pick out the same natural properties across all possible worlds. However, Horgan and Timmons set out a very influential challenge to Boyd. Their basic line of argument is that whereas twin earth thought experiments work to support scientific realism. The questions are intended to get the philosophy students thinking about these problems. They have used these kinds of questions in seminars as the questions set for seminars to spark conversation and discussion. The chapter also gives a cursory sketch of some of the ways in which philosophers have responded to the thought experiment.
