property dualism and epiphenomenalism as responses to the mind-body problem, including the threat to mental causation

What this dot point is asking

VCAA wants you to distinguish property dualism from substance dualism, explain why some philosophers move to it, and then evaluate it through the problem it generates: if mental properties are non-physical, do they do any causal work, or does the brain do everything while consciousness merely watches (epiphenomenalism)? The high-band answer keeps the substance/property distinction sharp, reconstructs the motivation from the explanatory gap, and weighs the cost of denying mental causation.

From substance dualism to property dualism

Substance dualism posits two substances, a thinking thing and an extended thing, and then struggles to explain how they interact. Property dualism keeps one substance, the physical body and brain, and locates the dualism in properties instead. A brain state has physical properties (mass, firing rate, chemistry) and, when it is a conscious state, also has phenomenal properties: the felt redness of red, the ache of a pain. These phenomenal properties are not identical to, and not reducible to, the physical properties, even though they belong to the same physical thing.

This is meant to be the best of both worlds. It honours the physicalist insistence that there is no ghostly extra substance, while honouring the dualist insight that consciousness is something over and above the merely physical facts.

The motivation: the explanatory gap

The driving argument is the explanatory gap, named by Joseph Levine. Reconstructed:

1. A complete physical description of the brain tells us about structure, function and dynamics.
2. No amount of structural and functional information entails what an experience feels like from the inside.
3. So there is a gap between the physical facts and the phenomenal facts.
4. The best explanation of the gap is that phenomenal properties are a further, non-physical kind of property.

David Chalmers calls this the hard problem of consciousness: even after we explain every function the brain performs, the question why any of it is accompanied by experience remains open. Property dualism answers that experience is a fundamental feature, not reducible to function.

Epiphenomenalism: the threat to mental causation

The trouble arrives when we ask what these non-physical properties do. Physics holds that the physical world is causally closed: every physical event has a sufficient physical cause. The brain event that is your pain already has a complete physical cause, and it produces your flinching through ordinary physical channels. So what is left for the non-physical phenomenal property to do? The natural answer is nothing. This is epiphenomenalism: mental properties are real, are produced by brain events, but are causally inert, like the smoke above a train that signals the engine without driving it.

Reconstructed as the problem:

1. The physical world is causally closed.
2. Phenomenal properties are non-physical.
3. If a non-physical property caused a physical event, either it would overdetermine an event that already has a sufficient physical cause, or it would violate closure.
4. So phenomenal properties cause no physical events.
5. Therefore property dualism collapses into epiphenomenalism.

Evaluation

Epiphenomenalism is deeply counter-intuitive. It seems obvious that I pull my hand back because it hurts, and that I report my experiences because I have them. If the feeling causes nothing, then the pain is not why I flinch, and my saying that I am in pain is not caused by the pain itself, which threatens to make our knowledge of our own experience mysterious. This is the self-stultification objection: if experiences are causally inert, it is unclear how I could ever come to talk or know about them.

The property dualist has replies. One is to bite the bullet and accept epiphenomenalism, treating the intuition of mental causation as an illusion produced by the reliable correlation between feeling and behaviour. Another is to deny strict causal closure or to argue that phenomenal and physical properties are two aspects of one event, so that the event causes the flinch and the phenomenal property is part of that cause (a dual-aspect or non-reductive view). A third is to point out that the rival, physicalism, only avoids the problem by denying the explanatory gap, which many find no less counter-intuitive than epiphenomenalism.

Judgement: property dualism is a real advance on substance dualism because it dissolves the interaction problem and takes the explanatory gap seriously. But it buys this at the price of mental causation: either it slides into epiphenomenalism, which makes nonsense of everyday psychological explanation and of our knowledge of our own minds, or it must weaken causal closure, which reintroduces a version of the very problem it was meant to escape. The view is coherent and well-motivated, but its causal commitments remain its unresolved weakness, so it is best treated as a serious contender rather than a settled solution.