Substance dualism (SD)
- [required] Section on dualism in chapter 2 of Paul M. Churchland (1984) Matter and consciousness : a contemporary introduction to the philosophy of mind MIT Press. Online preview at amazon. HKU ebook
- [Required] Chapter 7 on dualism. In Ming, Thomas; Wong, Ching Wa; Leung, Danny; Yung, Lawrence; Lau, Yen Fong (2006) Twenty Problems in Philosophy McGraw-hill preprint version on HKU intranet
- William Lycan (forthcoming) "Giving dualism its due"
Arguments in support of SD
The argument from doubt
- I cannot doubt that I exist.
- I can doubt that my body / brain exists.
- Therefore, I am distinct from my body / brain.
Compare: "Tomas is tall. Thomas is not tall. So Tomas is not the same as Thomas."
Intensional context : A predicate P(x) creates an intensional context iff it is possible that P(a) and P(b) have distinct truth-values even though a=b.
- Not intensional: "x is tall"
- Intensional: "Tom believes that x is tall"
The argument from indivisibility
Descartes, René. (1641). Meditations on First Philosophy. E. S. Haldane and G. R. T. Ross, trans. In The Philosophical Works of Descartes, Vol. 1. Cambridge: Cambridge University Press, 1970, p.196.
@When I consider the mind, that is to say, myself inasmuch as I am only a thinking thing, I cannot distinguish in myself any parts, but apprehend myself to be clearly one and entire.@
- My mind is not divisible.
- My body / brain is divisible.
- Therefore, my mind is distinct from the body / brain.
- Is the mind really indivisible?
- "Descartes cannot distinguish in himself any parts" => "Descartes does not have any parts"?
Arguments based upon paranormal phenomena
- Phenomenon X has been observed.
- X is best explained by SD.
- Therefore, SD is true.
Examples of X: testimonies of people seeing ghosts, communicating with the dead through a medium, out of body experiences
Arguments against SD
The argument from causal interaction
- The mind causally interacts with the physical world.
- SD cannot explain this causal interaction.
- Therefore SD is false.
- Parallelism - the mental and the physical do not interact.
- Explanatory failure does not imply falsity. Brute fact?
- Our best physical theories are non-deterministic, and so allows scope for non-physical causal interaction.
- SD violates physical laws such as the conservation of energy. See Main/DualismEnergy.
The argument from animal minds
- Whether a creature has a soul is an all-or-nothing matter.
- Whether a creature has a mind is not an all-or-nothing matter.
- Having a mind is not the same as having a soul.
Inference to the best explanation
- We should choose the theory that provides the best explanation.
- Physicalism provides a better explanation of the mind than SD.
- Therefore we should not accept SD.
What needs to be explained:
- Causal interaction between the mind and the world.
- Localization of brain functions - language, emotions, memory, personality, visual perception, facial recognition ...
Mutations of SD
What positions can a modern-day dualist retreat to?
- The mind as a distributed system - mental activities take place mainly in the brain, but some still occur in the soul. (But which ones?)
- The soul is an emergency backup system - normally functions as a memory backup, but activates when you die. (see ConsciousnessBuddhismLevels)
- Idealism - The "physical" world is a mental simulation, a product of consciousness (but whose?).