Baruch Spinoza was a 17th-century Dutch philosopher known for his groundbreaking ideas about God, nature, and the universe. He believed that everything in existence is interconnected and that God is not a separate entity but rather synonymous with nature itself. This view challenged traditional religious beliefs and laid the groundwork for modern philosophy. Spinoza's most famous work, the Ethics, presents his thoughts in a geometric style, using definitions and propositions. He emphasized reason and rationality, arguing that understanding the world through logic leads to true happiness. His ideas influenced later thinkers, including Immanuel Kant and Albert Einstein, making him a key figure in the history of philosophy.