What’s wrong with strong necessities?

Abstract

David Chalmers’ challenge to physicalism has dominated the philosophy of mind for the last 17 years. His 1995 paper ‘Facing up to the Problem of Consciousness’ and his 1996 book The Conscious Mind reinvigorated the debate between physicalists and dualists. But Chalmers’ mature attack on physicalism appeared over a decade later in his extensive 2009 paper ‘The Two-Dimensional Argument against Materialism’, reprinted in this volume. Chalmers’ argument against a posteriori physicalism starts with the conceivable separation of mind and brain. It makes conceptual sense that a being that who shares all my physical properties should nevertheless have no conscious life. Zombies are conceivable. Chalmers then aims to move from the conceivability of zombies to their metaphysical possibility. If this move is granted, it follows that physicalism is false. If it is metaphysically possible that a being share my physical properties but not my conscious properties, then my physical properties cannot metaphysically determine my conscious ones. But obviously the move from conceivability to possibility cannot be immediate. As Kripke’s work made clear, a statement can be conceivably true and yet not possibly true: ‘Water is not H2O’ is conceivably true and yet is true at no metaphysically possible world.