Stoicism is an influential Hellenistic philosophy, founded by Zeno of Citium in Athens around 300 BCE, that taught the universe operates by divine reason and offered a systematic approach to life. Its adherents, including Roman Emperor Marcus Aurelius, pursued a "well-reasoned life" through virtue, integrating logic, monistic physics, and naturalistic ethics to foster rational dialogue and harmony within the cosmos. A significant intellectual achievement was the development of propositional logic by Chrysippus in the 3rd century BCE, a system distinct from term logic and considered crucial for understanding ethics. Flourishing throughout the Greco-Roman world until the 3rd century CE, Stoicism declined after the rise of Christianity in the 4th century CE but has experienced notable revivals in the Renaissance and contemporary eras.