No strong necessities from radically opaque concepts

Abstract Philip Goff raises an ingenious objection to David Chalmers’s (2009) two-dimensional zombie argument in his 2014 paper (co-authored by David Papineau) ‘What’s wrong with strong necessities?’ The objection aims to defeat the conceivability-possibility thesis by arguing that strong necessities, necessary truths that can be conceived to be false, can be constructed by putting an identity sign between two co-referring radically opaque concepts, concepts that refer but reveal nothing about their referents. If Goff’s strategy succeeds, not only is the two-dimensional zombie argument defeated, but Chalmers’s modal monism must also be rejected. This paper aims to defend Chalmers’s zombie argument and modal monism against Goff’s objection. If internalism about reference fixing is true, I argue that no radically opaque concept can exist. If externalism about reference fixing is true, I argue that although radically opaque concepts can exist, strong necessities cannot be constructed by putting an identity sign between two such concepts. In conclusion, Goff’s attack fails to provide any further evidence for the existence of strong necessities, and, as a result, fails to pose any genuine threat to the two-dimensional zombie argument and modal monism.