George Berkeley – known as Bishop Berkeley – was an Anglo-Irish philosopher whose primary achievement was the advancement of a theory he called "immaterialism". This theory denies the existence of material substance and instead contends that familiar objects like tables and chairs are ideas perceived by the mind and, as a result, cannot exist without being perceived. Berkeley is also known for his critique of abstraction, an important premise in his argument for immaterialism.

A Treatise Concerning the Principles of Human Knowledge is a 1710 work, in English, by Irish Empiricist philosopher George Berkeley. This book largely seeks to refute the claims made by Berkeley's contemporary John Locke about the nature of human perception. Whilst, like all the Empiricist philosophers, both Locke and Berkeley agreed that we are having experiences, regardless of whether material objects exist, Berkeley sought to prove that the outside world is also composed solely of ideas. Berkeley did this by suggesting that "Ideas can only resemble Ideas" – the mental ideas that we possess can only resemble other ideas and thus the external world consists not of physical form, but rather of ideas. This world is given logic and regularity by some other force, which Berkeley concludes is God.