George Berkeley was an Irish philosopher born in 1685, best known for his theory of idealism. He argued that physical objects do not exist independently of our perception; instead, they only exist when they are being observed. This idea is often summarized by his famous phrase, "esse est percipi," which means "to be is to be perceived." Berkeley believed that everything we know about the world comes through our senses. Berkeley's work challenged the traditional views of John Locke and other philosophers of his time. He also contributed to the fields of epistemology and metaphysics, influencing later thinkers like David Hume and Immanuel Kant. His ideas continue to spark discussions in philosophy, particularly regarding the nature of reality and perception.