Substance dualism and Descartes' conceivability and divisibility arguments, property dualism and the philosophical zombies and knowledge arguments, and the objections to dualism including the problem of interaction, the conceptual problem of causation and the issues of other minds and category mistakes.

What this dot point is asking

AQA wants you to explain substance dualism and property dualism, set out the main arguments for dualism (Descartes' conceivability and divisibility arguments, and the property-dualist zombie and knowledge arguments), and evaluate the objections, above all the problem of interaction, together with the conceptual problem of causation, the problem of other minds and Ryle's charge of a category mistake.

Substance and property dualism

Descartes' arguments for substance dualism

The standard physicalist replies attack the bridging premises, and a good answer rehearses them. Against conceivability, the masked man fallacy charge: from the fact that I can conceive of my mind without conceiving of my body, it does not follow that mind and body are really distinct, any more than the fact that I can conceive of the masked man without conceiving of my father shows the masked man is not my father; conceivability tracks our concepts, not the underlying identity, especially for an a posteriori identity such as mind-brain. Against divisibility, physicalists deny the premise that the mind is indivisible: split-brain cases and the way damage to specific regions removes specific capacities suggest the mind has parts after all, and even if mental states seem indivisible, that may reflect how we describe them rather than their real nature.

Arguments for property dualism

• The philosophical zombies argument (Chalmers). A zombie is a being physically identical to a conscious person but with no conscious experience. If zombies are conceivable, and conceivability entails metaphysical possibility, then consciousness is not entailed by the physical facts, so phenomenal properties are non-physical.
• The knowledge argument (Jackson's Mary). Mary knows all the physical facts about colour vision while confined to a black-and-white room. On her release she learns something new (what it is like to see red). So there are non-physical facts (qualia), and physicalism is incomplete.

Objections to dualism

• The problem of interaction. If the mind is non-physical and unextended, how does it causally interact with the physical body (the will moves the arm; injury causes pain)? It is unclear how a non-spatial thing could push a physical one. Conservation of energy: if a non-physical mind injects energy into the brain, it seems to violate the closure of the physical world. Princess Elisabeth pressed exactly this against Descartes.
• The conceptual problem of causation. We can give no intelligible account of the mechanism by which immaterial events cause physical ones; causation between such radically different things seems unintelligible.
• The problem of other minds. If minds are private non-physical things, behaviour gives no certain evidence of them, so it is hard to know other minds exist (often answered by an argument from analogy or inference to the best explanation).
• The category mistake (Ryle). Treating the mind as a non-physical thing ("the ghost in the machine") wrongly puts the mind in the same category as the body; mind talk is really talk about behavioural dispositions. Ryle's analogy: a visitor shown the colleges, library and labs of a university who then asks "but where is the university?" has mistaken the category, treating the university as a further building. The dualist, Ryle says, makes the same error in expecting the mind to be a further thing alongside the brain and behaviour.

One escape route is to abandon interaction. Epiphenomenalism keeps non-physical mental properties but denies they cause anything physical: the brain causes behaviour, and consciousness is a causally inert by-product, like the whistle of a steam train. This dodges the energy-conservation worry but pays a high price, because it seems to make my pain irrelevant to my crying out, and it raises the question of how, if mental states are causally inert, we could even know or talk about them. The interaction problem is therefore not just a puzzle but a fork: either explain interaction (which dualists struggle to do) or deny it (which strains credulity), and a strong evaluation weighs that dilemma.