What were the main arguments in A Treatise Concerning the Principles of Human Knowledge?

In his major work, A Treatise Concerning the Principles of Human Knowledge (1710), the Irish philosopher George Berkeley argued that nothing exists except for spirits (minds) and ideas.1

Core Arguments

• Esse est percipi: Berkeley’s central doctrine is that for nonthinking beings, "to be is to be perceived". He argued that physical objects, such as tables and chairs, are merely collections of "sensible ideas" (sense-data) that exist only insofar as they are perceived by a mind.12
• Rejection of Matter: Berkeley rejected the existence of an imperceptible "material substrate" or "matter" that supposedly underlies objects, a concept he found contradictory. He argued that because all knowledge is derived from perception, it is impossible to conceive of something existing "behind" or independent of ideas.31
• Primary and Secondary Qualities: He dismissed the distinction between primary qualities (like motion or extension) and secondary qualities (like color or taste), asserting that both are equally dependent on the mind.21
• The Role of God: To explain why objects continue to exist when not perceived by humans, Berkeley argued that they are sustained in existence by the mind of God.1

Berkeley maintained that his immaterialism was a defense of common sense, asserting that he was simply describing what objects truly are rather than denying their existence.21