Conscious experience is constitutive of existence.
This entails the metaphysical theory known variously as 'mental monism' and 'subjective idealism'. Terms that denote mental things are referential by virtue of private ostensive definition. Terms that denote physical things are analytically defined and have no referential content. Ultimately, the concept of a physical substance that exists independently of any consciousness is incoherent. The real universe consists of a set experientiae.