George Berkeley

Anglo-Irish philosopher and bishop — author of A Treatise Concerning the Principles of Human Knowledge — who argued that material substance does not exist and that reality consists entirely of minds and ideas — the most radical empiricist idealist.

Creates subjective idealism — Berkeley's esse est percipi (to be is to be perceived) argues that physical objects exist only as perceptions in minds; there is no mind-independent matter; God guarantees the continued existence of the world by perceiving it constantly; this is the most radical conclusion from Lockean empiricism.