Mind-Body Problem
dualism · philosophy of mind
The question of how mental states relate to physical states — Descartes' dualism inaugurated the modern version.
In practice
A drug changes mood reliably. That establishes physical influence on the mental and leaves untouched the question of why the resulting state is experienced at all.
The common mistake
Treating the problem as settled by evidence that the brain produces the mind. Correlation between neural and mental states is agreed by every party; the dispute is over what that relation is.
The mind-body problem is the question of how mental states relate to physical states. Thoughts and sensations seem unlike anything physical, and they clearly interact with the body in both directions.
Descartes and the interaction difficulty
Descartes set the modern form in 1641. Mind is thinking and unextended; body is extended and unthinking. They are distinct substances, which explains why mental states appear so unlike physical ones.
The objection came immediately, from Princess Elisabeth of Bohemia in correspondence: if the mind has no extension and no physical properties, how does it move anything? Descartes pointed to the pineal gland, which names a location without explaining a mechanism. Causation between two substances sharing no properties has never received a satisfying account.
The physicalist options
Identity theory holds that mental states are brain states, in the way that lightning is electrical discharge. The objection is multiple realisability: creatures with different physiology might share a mental state, which they could not if the state simply were a particular neural arrangement.
Functionalism answers by identifying mental states with roles — a state caused by tissue damage, producing avoidance, is pain, whatever realizes it. This allows minds in different substrates and struggles with consciousness, since a role could be filled with nothing being experienced.
Eliminativism holds that beliefs and desires belong to a folk theory that a mature neuroscience will replace. Critics note that the position must be stated using the concepts it proposes to eliminate.
The residue
The functional questions have yielded steadily to research. The question of why any physical arrangement is accompanied by experience has not, which is why the hard problem is usually treated as the surviving core of the original puzzle.
Concept web
Open the full webQuestions
What is the mind-body problem?
The question of how mental states relate to physical states of the body and brain. Mental states appear to have properties unlike physical ones, yet the two clearly influence each other.
What is Cartesian dualism?
Descartes's view that mind and body are distinct substances — one thinking and unextended, the other extended and unthinking. Its central difficulty is explaining how two such different things interact.
What is functionalism in philosophy of mind?
The view that mental states are defined by their causal roles rather than their physical makeup. Pain is whatever is caused by damage and produces avoidance, which allows different physical systems to share mental states.