George Berkeley was born in 1685 in Ireland. He was an Anglo-Irish philosopher best known for advancing immaterialism, the theory that objects only exist insofar as they are perceived. According to Berkeley, there are only two kinds of things: spirits and ideas. Spirits are active beings that produce and perceive ideas, while ideas are passive beings that are produced and perceived. Berkeley argued that God is responsible for the existence of ideas since humans do not have direct control over what they perceive through their senses. He made important contributions to philosophy through works such as A Treatise Concerning the Principles of Human Knowledge. Berkeley died in 1753 in Oxford, United States from congestive heart failure.