Comparison
Dualism vs Materialism
Dualism and materialism give opposite answers to the oldest question about the mind. Dualists hold that consciousness involves something nonphysical. In René Descartes’s substance dualism, the mind is a thinking thing distinct from the extended body. Property dualists, including David Chalmers in his naturalistic dualism, keep one physical substance but give it irreducible mental properties. Dualism is also the default teaching of Judaism, Christianity and Islam.
Materialists hold that consciousness is entirely physical, a product of brains and bodies with nothing left over. It is the working assumption of most neuroscientists, and in the 2020 PhilPapers survey just over half of professional philosophers accepted or leaned toward physicalism.
The arguments run in both directions. Dualists point to the explanatory gap. In Frank Jackson’s thought experiment, Mary knows every physical fact about color but has never seen red, and she seems to learn something new when she first does. Chalmers argues that a physical duplicate of you with no experience, a ‘zombie’, is conceivable. Materialists answer with the interaction problem, first pressed on Descartes by Princess Elisabeth of Bohemia. If physics is causally closed, it is hard to see how a nonphysical mind could move a neuron. They add that brain damage and drugs change experience in precise ways, and that Occam’s razor counts against a second kind of thing.
Much rides on the outcome. Substance dualism leaves room for a soul to survive death, while materialism ties the mind’s fate to the brain’s.
Common ground. Both accept that in ordinary life experience depends closely on the brain. Interactionist dualists such as Karl Popper and the Nobel-winning neuroscientist John Eccles used the same brain science materialists rely on. The dispute is over whether that science tells the whole story.
Key differences
| Dualism | Materialism | |
|---|---|---|
| What the mind is | Something nonphysical, either a separate substance or irreducible mental properties of physical things. | Brain activity, its functional roles, or other physical processes, with nothing nonphysical involved. |
| Strongest argument | The explanatory gap. Mary’s room and philosophical zombies suggest physical facts leave experience out. | The tight dependence of experience on the brain, and the success of physical science everywhere else. |
| Main objection | The interaction problem. A nonphysical mind moving neurons seems to break the causal closure of physics. | The hard problem. A full account of neural activity seems to leave open why it feels like anything. |
| Testability | Hard to test directly, with no clear method for studying how a nonphysical mind works. | Testable at the level of mechanisms through neuroscience, though the hard problem itself resists experiment. |
| Life after death | Substance dualism allows a soul to outlive the body, one reason most religions hold it. | Consciousness ends when the brain stops working. |
| AI consciousness | Doubtful if minds are souls. Chalmers’s property dualism allows it for systems with the right functional organization. | Possible on functionalist and computational views, doubted on biological ones. |
On the big questions
| Dualism | Materialism | |
|---|---|---|
| AI consciousness | Yes or likely 2 Possible or depends 6 Uncertain 4 Unlikely or no 25 | Yes or likely 68 Possible or depends 54 Uncertain 34 Unlikely or no 18 |
| Life after death | Yes or likely 23 Possible or depends 7 Uncertain 1 Unlikely or no 6 | Possible or depends 6 Uncertain 3 Unlikely or no 176 |
| Mind uploading | Yes or likely 1 Possible or depends 2 Uncertain 4 Unlikely or no 30 Not needed (consciousness persists anyway) 1 | Yes or likely 59 Possible or depends 36 Uncertain 27 Unlikely or no 37 |
| Meaning and purpose | Cosmic or ultimate 27 Humanistic only 3 Uncertain 5 | Cosmic or ultimate 1 Humanistic only 154 Uncertain 11 |
Dualism
Consciousness requires something beyond the physical brain. A nonphysical mind or soul, distinct from matter, works together with the body, and in many versions it can survive the body’s death.
Materialism
Consciousness is entirely physical. Every experience is produced by brains and bodies, and ultimately by the particles and fields of physics, with nothing nonphysical left over.