Materialism
physicalism · materialist
The view that everything that exists is physical, so mental states are states of the brain and nothing further is required to explain them.
In practice
Anaesthesia works on the brain and removes experience reliably. That is the kind of evidence physicalism rests on, and it does not by itself explain why the brain produces experience at all.
The common mistake
Reading it as a claim that only matter exists. Modern physicalism counts fields, forces and whatever fundamental physics describes, which is why the name shifted.
Materialism — usually called physicalism now, since modern physics describes fields and forces rather than matter alone — holds that the physical is all there is. Minds are what certain physical systems do.
The versions
Identity theory. Mental states are brain states, in the way lightning is electrical discharge. The objection is multiple realisability: creatures with very different physiology might share a mental state, which they could not if that state simply were one neural arrangement.
Functionalism. Mental states are defined by their causal roles. Pain is whatever is caused by damage and produces avoidance, whatever realizes it. This handles multiple realisability and permits minds in other substrates. Its difficulty is qualia: a role could be filled with nothing being experienced.
Eliminativism. Beliefs and desires belong to a folk theory that mature neuroscience will replace, as phlogiston was replaced. Critics note the position must be stated using the concepts it proposes to eliminate.
The case for
Causal closure: every physical event appears to have a sufficient physical cause, leaving nothing for a non-physical mind to do. Dependence: brain damage changes the mind in specific, predictable ways. And the track record — phenomena that looked to require something extra, including life itself, have repeatedly turned out not to.
The case against
The explanatory gap. Even granting that mental states are physical, no account explains why those physical states are accompanied by experience. The knowledge argument and the conceivability of a being functionally identical to a person and entirely without experience are attempts to turn that gap into an argument.
Physicalists reply that the gap is in our concepts rather than in the world, and that the intuitions driving these arguments are unreliable guides to what is possible.
Where it stands
Physicalism is the majority position among philosophers of mind, held with open acknowledgment that consciousness is not yet explained on it. See dualism and mind-body problem.
Concept web
Open the full webQuestions
What is materialism in philosophy?
The view that everything that exists is physical, so mental states are states of the brain and require nothing beyond physical explanation. It is usually called physicalism now.
What is the difference between identity theory and functionalism?
Identity theory says a mental state is a particular physical state. Functionalism says it is whatever plays a given causal role, which allows different physical systems to share mental states.
What is the explanatory gap?
The objection that even if mental states are physical, nothing explains why those states are accompanied by experience. Physicalists reply the gap is in our concepts rather than in the world.