Believing In Twin Earth: New Evidence for the Normativity of Belief

According to many philosophers, the notion of belief is constitutively normative (Boghossian ( 2003 , 2005 ); Shah ( 2003 , 2006 ); Shah and Velleman ( 2005 ); Gibbard ( 2005 ); Wedgwood ( 2002 , 2007 )). In a series of widely discussed papers ( 1990 , 1992a , 1992b ), Terence Horgan and Mark Timmons have developed an ingenious ‘Moral Twin Earth’ argument against ‘Cornell Realist’ metaethical views which hold that moral terms have synthetic natural definitions in the manner of natural kind terms. In this paper we shall suggest that an adaptation of the Moral Twin Earth argument to the doxastic case – Doxastic Twin Earth – provides new evidence for the normativity of belief.