(noun) a theory holding that the self can know nothing but its own modifications and that the self is the only existent thing / (noun) extreme egocentrism
Sass describes solipsism as a state of mind in which 'the whole of reality, including the external world and other persons, is [regarded as] but a representation appearing to a single individual self'.
quoting Louis Sass, The Paradoxes of Delusion, 8