George Berkeley (1685–1753) was awash in the world of ideas. He believed that everything was an idea, even physical matter. Only minds and the ideas they generate are real, according to this Irish clergyman. He is considered to be the founder of the modern version of Idealism, a belief that goes back to Plato in its original presentation. Unlike the closet atheism of Locke, Berkeley flatly states that God is responsible for the introduction and dissemination of perceptions into the human brain. These things we perceive do not exist outside the mind. They have no substantial reality of their own.

His Treatise

Berkeley's major work is the Treatise Concerning the Principles of Human Knowledge. When a thunderous “Say What?!?” came forth from his philosophical peers, Berkeley attempted to give it a more populist spin in a version called The Three Dialogues Between Hylas and Philonous.

Berkeley's controversial philosophy was a response to the skepticism and atheism of the day. He lauded much of Locke's work but not the antispiritual element. Referring to Descartes's primary and secondary ideas (the mind and the physical world), Berkeley states that the only way to grasp the primary qualities is through the secondary qualities. And no matter how you look at it, it's all in your mind.

Direct and Indirect Perception

Berkeley made the distinction between direct perception and indirect perception. Direct perception is the sensory input of things, and indirect perception is how they are interpreted by the mind. Berkeley insists that we all exist in our subjective realities with language being the only thing that can bridge the gap between isolated realities. Hence, sensory experiences and communication through language are the only way we can know things. But, of course, there is one exception to the rule: God. Berkeley was once asked the age-old philosophical question, “If a tree falls in the forest and no one is there to hear it, does it make a noise?” Given his view of reality, you would think that the answer would be no. The answer is yes, according to Bishop Berkeley, because God is there to hear it.

Berkeley did not gain many converts with his outlandish notion, but he certainly prompted many a lively debate among those who get excited about discussing such mind-blowing matters.