The concept of qualia and the hard problem of consciousness, the knowledge argument (Mary) and the philosophical zombies argument against physicalism, and physicalist responses including the ability and acquaintance replies, the new knowledge of old facts response and the denial that zombies are genuinely conceivable.

What this dot point is asking

AQA wants you to explain what qualia are and why they raise the hard problem of consciousness, to set out the two anti-physicalist arguments built on them (Jackson's knowledge argument and Chalmers' philosophical zombies argument), and to evaluate the main physicalist responses to each.

Qualia and the hard problem

The knowledge argument (Mary)

The philosophical zombies argument

Physicalist responses to the knowledge argument

• The ability hypothesis. On release Mary gains a know-how (the ability to imagine, recognise and remember red), not a new propositional fact, so no non-physical fact is learned.
• The acquaintance reply. Mary gains a new acquaintance with redness, a new relation to a fact she already knew, not knowledge of a new fact.
• New knowledge of an old fact (the phenomenal concept strategy). Mary learns an old physical fact under a new (phenomenal) mode of presentation; there is one fact, grasped in two ways, just as one can know that water is wet without knowing that H2O is wet.

Physicalist responses to the zombie argument

• Deny conceivability entails possibility. That zombies seem conceivable shows only the limits of our concepts, not a genuine metaphysical possibility, just as "water without H2O" can seem conceivable yet is impossible.
• Deny zombies are genuinely conceivable. Once we fully grasp what fixing all the physical and functional facts involves, the idea of a duplicate that lacks consciousness is not really coherent.

How the two arguments relate

The knowledge argument and the zombie argument are best seen as two routes to the same anti-physicalist conclusion, attacking physicalism from different directions. The knowledge argument is epistemic: it starts from a gap in what can be known (Mary knows the physical facts but not the phenomenal fact) and infers a gap in what there is. The zombie argument is modal: it starts from a claim about what is conceivable and possible (a physical duplicate without consciousness) and infers that the phenomenal is not necessitated by the physical. Both turn on the idea that fixing the physical facts leaves the phenomenal facts open, which Chalmers calls the failure of supervenience. Jackson's later recantation is worth knowing: he came to accept a representationalist physicalism and to regard the knowledge argument as unsound, on the ground that what Mary acquires is a new representation of a physical property rather than acquaintance with a new property.

The decisive battleground for both arguments is the link between the epistemic or conceptual and the metaphysical. The phenomenal concept strategy is the most powerful physicalist response to both at once: it holds that we possess special phenomenal concepts that refer to physical brain states but do so in a distinctive, first-person way, so the existence of an explanatory gap (we can conceive the physical without the phenomenal) is explained as a feature of how we think, not as evidence of two kinds of property. If that is right, Mary gains a new phenomenal concept of a fact she already knew under a physical concept, and the zombie's conceivability is just the separability of two concepts of one property. The dualist replies that this either understates the explanatory gap or smuggles the phenomenal back in.