George Berkeley (12 March 1685 – 14 January 1753), also known as Bishop Berkeley (Bishop of Cloyne), is an Anglo-Irish philosopher whose primary achievement is the advancement of a theory he calls "immaterialism" (later referred to as "subjective idealism" by others).

This theory denies the existence of material substance and instead contends that familiar objects like tables and chairs are only ideas in the minds of perceivers, and as a result cannot exist without being perceived.

Thus, as Berkeley famously puts it, for physical objects "esse est percipi" ("to be is to be perceived").

Berkeley is also known for his critique of abstraction, an important premise in his argument for immaterialism.

In 1709, Berkeley publishes his first major work, An Essay towards a New Theory of Vision, in which he discusses the limitations of human vision and advances the theory that the proper objects of sight are not material objects, but light and color.

This foreshadows his chief philosophical work, A Treatise Concerning the Principles of Human Knowledge , in 1710 which, after its poor reception, he rewrites in dialogue form and publishes under the title Three Dialogues between Hylas and Philonous in 1713.

In this book, Berkeley's views are represented by Philonous (Greek: 'lover of mind'), while Hylas (Greek: 'matter') embodies the Irish thinker’s opponents, in particular John Locke.

Berkeley argues against Sir Isaac Newton's doctrine of absolute space, time and motion in De Motu (on Motion), published in 1721.

His arguments are a precursor to the views of Mach and Einstein.

In 1732, he publishes Alciphron, a Christian apologetic against the free-thinkers, and in 1734, he publishes The Analyst, an empiricist critique of the foundations of infinitesimal calculus, which is influential in the development of mathematics.

His last major philosophical work, Siris (1744), begins by advocating the medicinal use of tar water, and then continues to discuss a wide range of topics including science, philosophy, and theology.

Interest in Berkeley's work increasea after the Second World War, because he tackles many of the issues of paramount interest to philosophy in the 20th century such as the problems of perception, the difference between primary and secondary qualities, and the importance of language.