Metaphysical Solipsism

philosophy

Definition

Metaphysical Solipsism

Metaphysical solipsism is the strongest form of solipsism. It holds that only one’s own mind and its contents $M_S$ exist; the external world and other minds do not.

Formally, for a subject $S$ with mental contents $M_S$, metaphysical solipsism is the ontological claim

$$\{x:x\text{ exists}\}=M_S.$$

Everything apparently external — bodies, other subjects, the physical world — is taken to be content within $M_S$ rather than an independent entity.

Contrast with the Weaker Variant

Unlike epistemological solipsism, which grants that the external world may exist unprovably, metaphysical solipsism removes it entirely. The move is ontological: the world is not merely unknowable, it is not there. This makes it the limiting case against which ontology and perception theories are tested.