  Imagine a world—Moral Twin Earth—that is exactly like the actual world, except on Moral Twin Earth, people’s use of moral terminology is causally regulated by different properties from those in the actual world. People use moral terminology to praise and blame and to guide action, but they take very different kinds of actions to be worthy of praise or blame and they guide their actions in very different ways. Thus, if the causal reference theory is true for moral terms, the word ‘right’ literally means something different on Moral Twin Earth than it does in the real world—this is the common intuition that drives Putnam’s original Twin Earth case. But we do not have the same judgement about how people use moral language on Moral Twin Earth! If people on Moral Twin Earth take different actions to be worthy of praise or blame, we don’t conclude that our words ‘right’ and ‘wrong’ mean different things. We conclude that there is a substantive moral disagreement between the denizens of Moral Twin Earth and the people in our world, and that such disagreement is possible only because we and the Twin Earthers mean the same thing by our moral terms. Horgan and Timmons argue that this proves that moral terms like ‘right’ and ‘wrong’ do not refer to whatever it is that causally regulates their use. So much the worse for Cornell realism. (See Dowell (2016) for a recent, influential criticism of this argument).