A philosophy or worldview established by Greek philosopher Epicurus (341–270 BCE). (The term epicurean can also simply describe a person devoted to the enjoyment of good food and drink, without knowledge of the worldview that lent its name to this definition.) Foundational to epicureanism is the disbelief in an immortal soul. Epicurus advocated a simple life of freedom from fear, absence of bodily pain and modest pleasure. The major sources for this worldview are Lives of Eminent Philosophers written in Greek by Diogenes Laertius in around the 3rd century CE and De Rerum Natura (On the Nature of Things) by Lucretius in the 1st century BCE. Most of Epicurus’s own writing has not survived. Epicurus proposed that the goal of human life is happiness. He advised followers to eliminate fears and anxieties by living simply, being honest and avoiding politics and fame (among other aggravations) where possible. He believed friendship was a main source of happiness. The main rival Greek philosophy of the day, Stoicism, also advocated the simple life but for the Stoics living virtuously rather than seeking happiness was the goal. Epicureanism initially flourished in Ancient Greece and Rome before nearly vanishing in the 3rd century CE. It was revived during the European Enlightenment, and now has small communities of adherents around the world. Epicureanism has strongly influenced other worldviews, including humanism and freethought. Some figures strongly influenced by Epicureanism include philosophers Friedrich Nietzsche (1844–1900) and Karl Marx (1818–83), British naturalist Charles Darwin (1809–82), co-author of the American Constitution, Thomas Jefferson (1743–1826), and American writer and philosopher Ayn Rand (1905–79). One ritual associated with Epicureanism include celebrating the birth of Epicurus on the 20th day of each month.