In the philosophy of mind, monism is an answer to the mind-body problem, which holds that there is only one substance that exists, be it mind or body. The two main versions of the monist response to philosophy of mind are physicalism, which holds that only the body truly exists, and idealism, which argues that only the mind truly exists. The alternatives to monism are the various versions of dualism.
- Physicalism, including most commonly-held positions today, which asserts that the mind may be reduced to the physical processes of the brain.
- Behaviourism, which holds that talk about mental states can be reduced to talk about behaviours.
- Functionalism, which states that mental states are caused by behaviours, senses and other mental states.
- Type physicalism, which argues that mental states are equivalent to brain states.
- Idealism, which claims that the mind is all that exists.
- Phenomenalism, which reduces the physical world to perceptions which exist within the mind alone.
See: mind-body problem