39 theories

Dualism: theories of consciousness

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.

Open Dualism on the mapAll theories A–Z

Dualism splits reality into two kinds of thing, physical and nonphysical. In its classic form, substance dualism, the mind is a separate nonphysical entity, usually called a soul, that works with the brain without being part of it. It is the most widely held view of consciousness in the world, the default teaching of Judaism, Christianity and Islam, and it has deep roots in Plato and in Indian schools such as Sāṃkhya and Nyāya.

René Descartes gave it its modern shape. Mind is thinking, unextended substance, body is extended, unthinking substance, and the two meet in the brain, at the pineal gland in Descartes’s account. Interactionists such as Karl Popper and John Eccles, and more recently Richard Swinburne, hold that mind and brain act on each other in both directions. Epiphenomenalists let the brain cause experience but deny that experience causes anything in return.

Other versions soften the split. Property dualism keeps a single physical substance but gives it irreducible mental properties, and David Chalmers’s naturalistic dualism adds psychophysical laws linking the two. William Hasker’s emergent dualism has the brain generate a nonphysical self. A separate lineage running from Aristotle through Aquinas to Eleonore Stump and Edward Feser treats the soul as the form that organizes a living body, and it sits here because it refuses to reduce mind to matter.

Most professional philosophers reject dualism. The main charge is the interaction problem. If physics is causally closed, with every physical event fully caused by earlier physical events, it is hard to see how something nonphysical could move a neuron. Dualism also adds a second kind of stuff that Occam’s razor would cut, and it offers no clear method for learning how souls work.