Monism

Monism is the philosophical view that only one sort of stuff in the universe exists ultimately. Monism is to be distinguished from dualism, which holds that ultimately there are two kinds of stuff, and from pluralism, which holds that ultimately there are many kinds of stuff.

There are three kinds of monism:

1. Physicalism or materialism, which holds that only the physical is real, and that the mental can be reduced to the physical
2. Idealism or phenomenalism, which holds the converse
3. Neutral monism, which holds that both the mental and the physical can be reduced to some sort of third, more "neutral" kind of stuff

See also: Reduction (philosophy), reductionism