---
title: Philosophy of Mind
section-id: metaphysics
sort: 140
author: Prof. James Okafor
created: 2026-02-12 09:00
modified: 2026-03-20 11:00
language: en
description: The mind-body problem, consciousness, and the hard problem.
---

# Philosophy of Mind

The mind-body problem asks how mental states—experiences, thoughts, desires, intentions—relate to physical states of the brain and body. This is one of the oldest and most contested questions in philosophy, and recent decades have seen it addressed from philosophy, neuroscience, and cognitive science simultaneously.

## Dualism

Descartes held that mind and body are distinct substances. The mind is a thinking, non-extended thing; the body is an extended, non-thinking thing. This **substance dualism** preserves the intuitive idea that consciousness is fundamentally different from anything physical.

Dualism faces the **interaction problem**: if mind and body are distinct substances, how do they interact? When I decide to raise my arm, a mental event causes a physical event. But mental events, on the Cartesian picture, are not physical; they have no location, mass, or energy. How can something non-physical act on something physical?

Attempts to solve the interaction problem—parallelism (God maintains a synchrony between mental and physical), occasionalism (God directly causes each physical event in response to mental events)—tend to invoke substantial theological machinery.

## Physicalism

Physicalism holds that everything, including the mind, is physical. Mental states are, or are constituted by, physical states of the brain.

### Identity Theory
Type identity theory holds that each mental type (pain, belief, desire) is identical to a physical type (a type of brain state). Pain is C-fibre firing. This is a bold and clean thesis, but it faces the **multiple realisability** objection: pain can be realised in different physical systems (humans, octopuses, possibly silicon-based systems). If pain is identical to C-fibre firing, then only C-fibres can be in pain. But this seems too restrictive.

### Functionalism
Functionalism holds that mental states are defined by their functional roles—their causal relations to inputs, outputs, and other mental states—rather than by their physical constitution. Pain is whatever state is caused by tissue damage, causes distress and avoidance behaviour, and interacts with beliefs and desires in the relevant ways. This handles multiple realisability: anything that plays the right functional role is in pain, regardless of its physical substrate.

Functionalism is the dominant view in philosophy of mind and cognitive science. It grounds the possibility of artificial intelligence: if a system plays the right functional roles, it has mental states.

### Problems for Functionalism
Ned Block distinguished **access consciousness** (information being available for reasoning, reporting, and guiding behaviour) from **phenomenal consciousness** (the ‘what it’s like’ quality of experience). Functionalism may account for access consciousness but struggles with phenomenal consciousness.

Frank Jackson’s **knowledge argument** (Mary’s room): Mary is a brilliant neuroscientist who knows every physical fact about colour vision but has lived her entire life in a black-and-white room. When she leaves and sees red for the first time, does she learn something new? Intuitively, yes—she learns what red looks like. If so, there are facts about conscious experience that are not captured by physical facts.

## The Hard Problem of Consciousness

David Chalmers distinguished the **easy problems** of consciousness (explaining cognitive functions: attention, integration, reporting) from the **hard problem**: why is there subjective experience at all? Why is there something it is like to see red, rather than the relevant information-processing occurring ‘in the dark’?

The easy problems are not truly easy; they may take decades to solve. But they are tractable in principle: they ask for functional explanations of mechanisms. The hard problem resists this treatment because any functional explanation seems to leave the subjective quality unexplained.

### Responses to the Hard Problem

- **Type-B physicalism**: Consciousness is physical, but the connection cannot be known a priori. The explanatory gap is epistemic, not metaphysical.
- **Illusionism**: Daniel Dennett and Keith Frankish argue that phenomenal consciousness as we conceive it is an illusion—our introspective reports misrepresent what is actually happening.
- **Panpsychism**: Consciousness is a fundamental feature of reality, present (in some form) wherever there is matter. Complex consciousness is the result of simple forms of experience combining. This dissolves the hard problem by making consciousness as basic as mass or charge.
- **Mysterianism**: Colin McGinn holds that the human mind is constitutively unable to solve the hard problem. We have the concepts required to pose it but lack the cognitive equipment to resolve it.

## Summary

- Dualism holds that mind and body are distinct substances; it faces the interaction problem
- Identity theory identifies mental types with brain types; it faces multiple realisability
- Functionalism defines mental states by functional role; it dominates cognitive science but struggles with phenomenal consciousness
- The hard problem distinguishes the subjective quality of experience from functional explanation
- Responses include type-B physicalism, illusionism, panpsychism, and mysterianism
