Substance Dualism 25 Marker

Is substance dualism a successful theory of mind?

Statement of Intent: SD is NOT a successful theory of mind for the following reasons:

  1. Cartesian SD cannot give an adequate account of the causal role of the mind – this is true from a conceptual perspective

  2. Interactionist forms of SD are not compatible with what we know empirically and would require us to give up fundamental principles of physics

  3. Non-interactionist forms of SD fail to explain self-knowledge making the theory deeply counterintuitive and leading to the unattractive conclusion that our beliefs about our mind are unreliable and unjustified

AO1 paragraph

what does SD claim, Cartesian dualism (essential properties, mental properties are properties of a mental substance, exist independently), non-identity of these two substances via conceivability and indivisibility, outline indivisibility and Leibniz’ principle, outline conceivability briefly, Cartesian Dualism is an interactionist, outline epiphenomenalist claim

SD claims that there are two separate and distinct substances – mind and body. Cartesian substance dualism claims that a) the essential property of body is extension while the essential property of mind is thought, b) mental properties like beliefs, desires and so on are properties of mental substance, and c) minds can exist independently of bodies (qua substance, mind is ontologically independent). Descartes aims to establish the non-identity of these two substances through his indivisibility and conceivability arguments. His indivisibility arguments uses the essential properties of mind and body to argue that mind is essentially unified and indivisible while body is not essentially unified and is divisible. Drawing on Leibniz’s law of the indiscernibility of identicals which states that if x and y are identical, then x and y have all their properties in common, Descartes concludes that because mind and body have different properties, they are not identical and must be separate and distinct. Descartes’ conceivability argument argues that it is conceivable for mind to exist without body, therefore it is metaphysically possible for mind to exist without body, therefore mind and body are distinct substances.

Cartesian SD also claims that mind and body can causally interact and is therefore an interactionist form of SD. Non-interactionist forms of SD include epiphenomenalist SD which claims that mental substance is not casually efficacious- mental events are merely by-products of physical processes (epiphenomena) and do not cause either physical events or other mental events.

RICE 1

R – Descartes wants to claim that mind and body causally interact with one another but Cartesian SD fails to give an adequate account of the causal role of the mind. This is clearly illustrated with the Conceptual Interaction problem first outlined by Princess Elisabeth of Bohemia. It is not clear how a mental substance, which is not extended and has no physical force can effect a physical substance which is extended and is moved by physical forces. Only something that is extended and can touch the thing that is moved can exert such a force.

I - Descartes argues that this objection fails because it relies on an inaccurate account of why things move. Example of how we might explain why something falls in terms of its weight. But weight does not ‘push’ the object whose weight it is. Instead, weight is the result of the force of gravity on the mass of an object and gravity is a force of attraction that operates without needing contact between two physical objects.

C – The conceptual interaction problem remains even if we amend the argument in light of Descartes’ response. A physical force would still need to be located in space but Descartes wants to maintain that the mind is not located in space so the conceptual interaction problem remains.

E – Elisabeth’s argument would show that there is a conceptual interaction problem if we try to understand the mind’s power to act on physical objects in terms of how physical objects act on each other. But this may not be the appropriate approach. As a result, this objection does not definitively show that interactionist forms of SD fail.

RICE 2

R - A more compelling reason why SD is not a successful theory of mind is that it is not compatible with what we know empirically. We can first show this by what we know of neuroscience. While we have evidence of bodily movements being cause by neuro-physical events, we do not have evidence of neuro-physical events being caused by mental events.

I - The substance dualist could respond to the objection by pointing out that we also do not have evidence against the claim that neuro-physical events are caused by mental events. The empirical evidence is therefore not against SD.

C- A more pressing empirical concern relates to how the interaction between mind and body would require us to accept that the law of conservation of energy is false (the empirical interaction problem). In a closed physical system (like the physical universe), the total amount of energy must remain constant according to the law of conservation of energy. If the mind moves the body, then a non-physical cause would transfer energy into the closed system and the law of conservation of energy would not apply to the physical universe. This would mean that physics could not give us a complete and correct account of physical energy in the universe.

E- Interactionist forms of SD are not attractive as they would involve contradicting fundamental principles in physics.

RICE 3

Although SD may try to sidestep both the conceptual and empirical interaction problems by claiming that mental substance and physical substance do not causally interact, epiphenomenalist forms of SD are also problematic in that they cannot account for self-knowledge.

ESD claims that mental events are causally inert and do not cause physical events or other mental events. Instead mental events are by-products of physical processes (epiphenomena). Part of the reason why this theory is unsuccessful is that this view of mental events seems very counterintuitive - we usually take the view that we experience causal connections between our mental states, and between our mental states and our behaviour, e.g. feeling pain leads to us clutching our leg or saying ‘my leg hurts’.

The most worrying implication of ESD however is that it leaves us alienated from beliefs about our own mind. We tend to think the following: I know I am in pain because my belief that I am in pain is caused by my sensation of pain (a mental state). But if ESD is true, then my mental state of pain causes nothing. I could have the belief that I am in pain regardless of whether I experience the sensation of pain. My beliefs about my own mind are therefore unjustified and unreliable. A theory which leaves us unable to account for self-knowledge in this way is deeply unappealing, and has negative consequences for how we relate to ourselves and our interactions with the world.

Conclusion

In my essay, I have shown that Interactionist forms of SD suffer from the conceptual interaction problem, and although the Substance dualist may question the methodology of understanding this interaction in terms of physical interaction, this does not show that the theory is true. Interactionist forms also emerge as fundamentally incompatible with what we know empirically. Epiphenomenalist forms of SD may avoid the conceptual and empirical problems but face the crucial problem of failing to account for self-knowledge. SD (in all forms) has been shown to be an unsuccessful theory of mind