Ockham rejected Plato's proof of God's existence. Leibniz's Principle of Sufficient Reason states that nothing happens without a reason. Stoicism was the most successful and longest lasting school of philosophy in Greco-Roman antiquity. African tribal societies believed that spirits or ancestors inhabited natural entities. Machiavelli and Hobbes broke with Aristotle's equation of politics and ethics. Shiva is considered the Hindu god of destruction.