Dualism holds that mind and the physical are fundamentally distinct — that a complete account of the physical world leaves something out. It is one of the oldest and most persistently attractive positions in philosophy of mind, drawing strength from the apparent irreducibility of conscious experience to anything merely physical. In its various forms, it has been defended by Descartes, Chalmers, and many contemporary philosophers who find physicalist accounts of phenomenal consciousness inadequate.
Substance vs. Property Dualism
Substance dualism (Descartes) holds that mind and body are two different kinds of stuff, res cogitans and res extensa, leaving the interaction problem that has dogged the view ever since. Almost no contemporary philosopher defends it.
Property dualism is the live form. It grants one kind of substance (the physical) but holds that conscious experience involves a further, irreducible kind of property — phenomenal properties not entailed by, or reducible to, the physical facts. Chalmers’s “naturalistic dualism” is the sophisticated version: one world, physically causally structured, but with phenomenal properties added as further fundamental features, connected to the physical by psycho-physical laws. See Physicalism.
The Case for Dualism
Dualism draws strength from a convergence of genuinely powerful intuitions, each of which feels like a discovery: the conceivability of philosophical zombies, the apparent gap in Mary’s knowledge, the explanatory gap between physical description and felt quality. Each is real as an epistemic phenomenon. The dualist inference reads these epistemic facts as ontological ones: because we cannot see how the physical explains the phenomenal, the phenomenal must be something over and above the physical. This inference from explanatory gap to ontological gap is the load-bearing move in every major contemporary dualist argument. See Zombies and Conceivability, Mary's Room, and The Explanatory Gap.
The Standard Pressure: Mental Causation
The best-known objection to property dualism runs through causation. If the physical world is causally closed, so that every physical event has a sufficient physical cause, then irreducible phenomenal properties risk having no work to do — a consciousness that watches but never steers (epiphenomenalism). Property dualists respond by accepting epiphenomenalism, by denying closure, or by reworking the causal story; each option carries a known cost, and Chalmers, to his credit, has explored them all candidly.
My View
The epistemic gap is real but lodged in us and our concepts, not in the world (see The Hard Problem of Consciousness). The inference from “we can’t explain how” to “it must be non-physical” is the unearned step that does all the dualist’s work. Two moves block it: the transparency of experience and the identity claim deflate the qualia-as-intrinsic-inner-properties picture the zombie and knowledge arguments require; and the phenomenal concept strategy explains why the gap should feel exactly this unbridgeable even if physicalism is true. Frank Jackson later abandoned the knowledge argument and became a physicalist, chiefly because epiphenomenalism made our knowledge of phenomenal properties self-stultifying; his mature route differs from this book’s transparency, identity, and phenomenal-concept strategy. See Jackson.
My own position (physicalism, reductive but non-eliminative and relational) is offered not as a denial of the dualist’s data but as a better home for it. The felt character of experience is preserved, as world-presenting representational content, without a second substance, a second kind of property, or irreducible psycho-physical laws. See Identity Theory and Intentionalism.
Related Concepts
- Physicalism — the broad physicalist alternative my view defends
- The Hard Problem of Consciousness — the epistemic-not-ontological framing that defuses the dualist inference
- The Explanatory Gap — Levine’s careful version of the gap dualism over-reads
- Zombies and Conceivability — the conceivability-to-possibility slide that powers modal arguments for dualism
- Qualia — the intrinsic-inner-property picture dualism needs and my view denies