George Berkeley (1685-1753) was an Irish philosopher who contributed to various areas of philosophy, most notably epistemology.

Berkeley was born into a noble family in Kilkenny, Ireland. He earned a Master's degree in Dublin and remained there to teach. Later, he earned a doctorate in divinity from the Church of Ireland.

His early works were in mathematics, though he eventually contributed to epistemology and metaphysics. His first prominent work, An Essay Towards a New Theory of Vision was published in 1709 and remains imporant to the study and current theories of optics.

Berkeley went to America in 1728 with the intention of founding a college there, but returned to England in 1732 when he was unable to finance his project.

The University of California, Berkeley and, by extension, Berkeley, California are named after George Berkeley.

Immaterialism

Chief among Berkeley's work is his development of immaterialism, a theory in epistemology which explains that human beings do not obtain knowledge about material objects. Instead, the only knowledge we have is of our ideas about objects, such as the sensations we perceive. Our perception of a material object is the entirety of our knowledge about it, whether or not our perception is truly representative of any real material thing.

Berkeley holds that esse est percipi — “to be is to be perceived”. This notion, which is a part of his immaterialism, holds that ideas exist only in the mind, and do not correspond to some external entity (such as the forms of Plato).

Berkeley's immaterialism is essentially an extension of the ideas of John Locke. Locke held that our experiences of objects can be divided into two parts: primary qualities, such as form, solidity and mobility, which are representative of a real object; and secondary qualities, such as colour and taste, which exist solely in our perception of an object. (For example, a red rose is not actually red, but only has certain primary qualities in its composition which produce the secondary quality of redness in our perception. In the absence of light, or in different light, the rose ceases to be red despite the fact that nothing about the rose changes.) Berkeley argues that Locke's empiricism is incomplete — he has no basis from his experiences for his certainty that our perception of primary qualities is accurate, or that we come to know anything about a real object at all.

For Berkeley, the idea or thought about an object is our complete knowledge about it. We have no valid reason for assuming that our idea corresponds to any actual object, or that a world external to our mind exists at all.

Berkeley's immaterialism is also known by the name “subjective idealism”.

Works

• An Essay Towards a New Theory of Vision (1709)
• A Treatise Concerning the Principles of Human Knowledge (1710)
• Three Dialogues Between Hylas and Philonous, In Opposition to Sceptics and Atheists (1713)
• The Analyst (1734)
• The Querist (1735)