Book excerpt: "All are lunatics, but he who can analyze his delusions is called a philosopher." -Ambrose Bierce, Epigrams If a tree falls and no one hears it, does it make a sound? I Used to Know That: Philosophy examines this and many other related questions. Spanning over some two-and-a-half thousand years of philosophical thought, this book covers the main highlights, from Pythagoras and Heraclitus, to Socrates, Plato, and Aristotle, to Descartes, Kierkegaard, Marx, and Sartre. From the Socratic method to structuralism, you'll get an overview of all the major theories, presented in an easy-to-understand and engaging format. This lively, fun-to-read compendium explains how philosophy began and uncovers the thinkers and movements that have used it in both brilliant and frightening ways. It includes: Short biographies of all the great philosophers, from the early Greeks to the modern greats All the main -isms and -ologies, from atomism to utilitarianism, via epistemology and ontology Quips, quotes, and conundrums to impress your friends at your next dinner party So if you ever paused to wonder about the origin of the phrase "platonic love" or why Nietzsche came to believe that "God is dead," this is the book for you. It will refresh and enlighten you, and it may even make you stop and reflect on the larger questions of life. Because after all, as Socrates said, "the unexamined life is not worth living."