monism

Monism is a philosophical position that asserts there is only one kind of fundamental substance or principle underlying reality. It stands in contrast to dualism, which divides reality into two kinds of substances (for example mind and matter), and to pluralism, which posits many substances or primes. In monistic theories, all phenomena—physical, mental, and experiential—derive from this single underlying reality.

There are several varieties. Materialist or physicalist monism holds that only physical substance exists; mental states are ultimately physical processes in the brain. Idealist monism claims that mind or consciousness is the fundamental reality and that matter is an appearance or construct. Neutral monism posits a single substance that is neither mental nor physical in itself but manifests as both; mental and physical properties are two sides of the same underlying stuff. In some traditions, such as Spinoza’s philosophy, a single substance (often identified with God or Nature) has infinite attributes, of which thought and extension are two.

Historically, monism appears in ancient Indian philosophy (Advaita Vedanta teaches non-dual unity of Atman and Brahman) and in Western thought with Parmenides’s claim that reality is one, and Spinoza’s substance monism. In modern times neutral monism has been associated with philosophers such as Bertrand Russell.

Critics of monism argue that it may struggle to account for the apparent multiplicity of things, change, and especially the subjective character of experience. Proponents respond that multiple aspects can reflect a single underlying reality.