1. Learning objective: To understand the objection that even if a zombie world is conceivable it may not be possible, and to evaluate how convincing this objection is.

2. Objection 2 Objection – they are not metaphysically possible Zombie worlds are not logically contradictory, and therefore conceivable, but is not a genuine metaphysical possibility.

3. Can we imagine that this water had a different chemical composition? Consider – Is water = H2O an analytic truth? Could people in the past have thought something different?

4. Can we conceive that water is not H2O? We could surely imagine that this liquid had a different chemical composition? But, what would we really be imagining? It would be a different liquid. So it is not metaphysically possible for H2O to be any other liquid, even if it perhaps is conceivable.

5. Saul Kripke If A = B, then and A and B are the same It is not possible for A to be B and B not to be A. A would be B in every possible world Kripke says identity claims are necessarily true (true in all possible worlds)

6. So… We can conceive of water not being H2O but it is not possible for water not to be H2O How does this relate to the zombie argument?

7. If phenomenal properties just are functional ones then it is not possible for zombies to exist. If physicalism is true, it is not possible for them to exist, even if it is conceivable. We cannot always infer possibility from conceivability

8. How does this relate to Smart’s ‘two concepts’? How might a PD reply?

9. The analogy does not work – water has a particular structure The essence of a physical property is its physical structure Whereas phenomenal properties are what it is like to experience something If these have different essences, they can exist independently Only essential properties of something can’t change in different possible worlds, contingent ones can.

10. Is this more or less persuasive than the objection that philosophical zombies are not conceivable?