Dr. Johnson thought he could refute an entire philosophy by kicking a stone.
George Berkeley was an 18th-century Irish Anglican bishop who developed one of philosophy's most radical theories: that material objects don't actually exist. Born in 1685 into the scientific revolution era of Newton and Locke, Berkeley studied at Trinity College Dublin and became a fellow there before traveling extensively in Europe and eventually becoming Bishop of Cloyne. His philosophical system, called idealism or immaterialism, argued that what we call physical objects are actually just collections of sensory ideas - colors, smells, textures, tastes - that exist only when perceived by minds. An apple, for Berkeley, is nothing more than the bundle of redness, sweetness, and crunchiness we experience. He built this theory partly in response to John Locke's empiricism, which held that we know the world through sensory ideas that represent external material objects. Berkeley argued this was unnecessary and problematic - if we only ever experience ideas, why assume material objects exist behind them? His famous principle was that for sensory objects, 'their esse is percipi' - their very essence is to be perceived. Berkeley saw his idealism as the best defense against atheism, since it made God necessary as the source of our consistent, orderly sensory experiences. Without material objects to cause our perceptions, only an all-perceiving divine mind could account for the regularity of nature. He also criticized Newton's concepts of absolute space and time as potentially atheistic. His first major work was 'A New Theory of Vision' (1709), followed by 'Principles of Human Knowledge' (1710) and 'Three Dialogues' (1713). Later works included 'De Motu' (1721), critiquing Newtonian mechanics, and 'Siris' (1744), connecting tar water's medicinal properties to philosophical reflections on the ether. Contemporary reception was mixed - his scientific work was respected, but his idealism was often ridiculed, famously by Samuel Johnson who kicked a stone claiming to refute Berkeley 'thus.' Berkeley responded that Johnson's bruised toe was just another sensory experience, not proof of matter. His ideas influenced David Hume significantly and contributed to later philosophical developments including Kant's transcendental idealism. Though his specific arguments fell from favor, Berkeley established idealism as a permanent philosophical position and raised enduring questions about the relationship between mind and reality.
