Hellenistic Philosophy

Among all the philosophical schools of Antiquity, none exercised so prolonged and so diverse an influence as Stoicism. Founded in Athens around 300 BCE by Zeno of Citium, Stoicism spanned five centuries, shaped Roman law, infiltrated early Christianity, and resurfaced powerfully in the Renaissance, the Enlightenment, and — more recently — in cognitive-behavioral therapy and philosophical self-help movements. The reason for this longevity is simple: Stoicism offers a coherent and practicable answer to the most urgent question of human existence — how to live well in a world we do not control. ...

Chrysippus of Soli (c. 280–c. 207 BCE) was the third scholarch (head) of the Stoic school in Athens and is considered, alongside Zeno of Citium, the second founder of Stoicism. While Zeno founded the school and established its fundamental theses, it was Chrysippus who systematically elaborated Stoic logic, physics, and ethics, producing a monumental body of work that ancient tradition estimated at over 700 titles — almost all now lost. What we know of his thought comes from secondary sources: Diogenes Laërtius, Plutarch, Cicero, Sextus Empiricus, and Epictetus. ...

Cicero Roman philosopher, orator, and statesman. The most important figure in transmitting Greek philosophy to the Latin world. His eclecticism synthesized Epicureanism, Stoicism, and the skepticism of the New Academy. He coined much of the Latin philosophical vocabulary — essentia, qualitas, moralis — that shaped all subsequent Western philosophy. Key Concepts Natural law: there is a universal moral law, grounded in reason, that transcends the positive laws of each people — the foundation of Western natural law theory Res publica: the republic as “the people’s affair” (res populi); the state is only legitimate when it serves the common good and respects the law Duty (officium): ethical life consists in fulfilling duties arising from reason, human social nature, and the roles each person occupies — systematized in De Officiis Academic probabilism: influenced by the skepticism of the New Academy, he argues that in the absence of certainty we should act according to what seems most probable (verisimile) Humanitas: the ideal of full human formation combining philosophy, rhetoric, and civic virtue; the Roman equivalent of the Greek paideia Highest good (summum bonum): debate among schools — for Stoics, virtue; for Epicureans, pleasure. Cicero leans toward Stoicism but presents arguments from all schools Influenced by Plato and Aristotle — politics, ethics, theory of knowledge Zeno of Citium — Stoicism (cosmopolitanism, natural law, duty) Epicurus — addressed critically Carneades — skepticism of the New Academy Influenced Augustine and all medieval philosophy — Latin vocabulary and natural law Thomas Aquinas — natural law theory Machiavelli, Montesquieu, Rousseau — republican theory Locke and Kant — natural rights and moral duty Renaissance humanism — ideal of humanitas Works On the Republic (De Re Publica, 54 BC); On the Laws (De Legibus, 52 BC); Tusculan Disputations (Tusculanae Disputationes, 45 BC); On Duties (De Officiis, 44 BC); On the Nature of the Gods (De Natura Deorum, 45 BC). ...

Diogenes of Sinope “Diogenes the dog” (kynikós) — refoundaer and principal figure of Cynicism. He lived in a large ceramic jar (pithos) in Athens, reduced his needs to a minimum, and despised all social convention. He said he sought “a human being” (ἄνθρωπον) walking with a lantern lit in broad daylight. When Alexander the Great offered to grant him any desire, he asked only that he step out of his sunlight. He embodied radical anticultural philosophy: virtue requires total self-sufficiency, not abstract philosophy. ...

Epictetus Phrygian ex-slave; the Stoic who most lived what he preached. His central distinction structures all Stoic ethics: what depends on us (eph’ hêmin: thoughts, impulses, judgments, desires) vs. what does not depend on us (ouk eph’ hêmin: body, fame, wealth, health). Inner freedom is absolute and cannot be taken by any master. “Bear and forbear” (anékhou kai apékhou). Born in Hierapolis, in Phrygia (modern Turkey), Epictetus spent his early years as a slave in Rome, in the service of Epaphroditus, a freedman connected to Nero’s court. It was in this setting that he studied under the Stoic Musonius Rufus, from whom he inherited the conviction that philosophy is worth only as much as it transforms conduct. He is said to have been lame — a condition he reportedly mentioned with serene indifference, a living example of his doctrine that disability touches the body, not the prohairesis, the will that chooses. Freed later in life, he devoted himself to teaching in Rome until the emperor Domitian expelled the philosophers from the city; he then moved to Nicopolis, in Epirus (northwestern Greece), where he founded a school that drew disciples from far and wide, including young men of the Roman elite. ...

Epicurus Born on the island of Samos around 341 BCE, Epicurus founded in Athens, in 307 BCE, the school known as the Garden (Kepos) — a community of friends that, remarkably for its time, welcomed women and slaves. He lived simply and in seclusion, and died around 270 BCE, facing with serenity the pains of a kidney ailment. His philosophy, heir to Socrates in the ideal of philosophy as an art of living, has a therapeutic aim: to free the human being from what disturbs their peace. ...

Lucretius (Titus Lucretius Carus) Roman poet and philosopher, author of De Rerum Natura (On the Nature of Things), the greatest philosophical poem of Antiquity. He systematized in Latin verse the physics and ethics of Epicurus, becoming the primary source for our knowledge of ancient Epicureanism. He defended atomism as an explanation of the universe, the mortality of the soul, and liberation from the fear of gods and death through rational understanding of nature. ...

Marcus Aurelius Marcus Aurelius Antoninus ruled Rome from 161 to 180 CE and is remembered as the last of the “Five Good Emperors” and as the most celebrated example of the ancient ideal of the philosopher-king. Adopted into the line of succession by Antoninus Pius, he received a careful education and turned early to Stoicism, above all through reading Epictetus, to whom he had been introduced by his teacher Junius Rusticus. His reign, far from peaceful, was beset by wars on the Danube frontier, by revolts, and by the devastating Antonine Plague — circumstances in which his philosophy proved less a doctrine than a discipline of inner survival. ...

Plotinus Born around 205 CE, probably in Roman Egypt, Plotinus studied for years in Alexandria under the enigmatic master Ammonius Saccas and later settled in Rome, where he founded a school and led a life of remarkable asceticism. His lessons were gathered and organized by his disciple Porphyry in the Enneads. He is the founder of Neoplatonism and the greatest philosopher of late antiquity, making Plato the starting point of one of the most grandiose metaphysics ever conceived. ...

Pyrrho Founder of Ancient Skepticism. Accompanied Alexander the Great to India and encountered ascetics who influenced his thought. Left no writings; lived coherently with epoché. Tranquility (ataraxia) arrives naturally when one suspends all judgment: since we cannot know whether something is good or bad, beautiful or ugly, there is no reason for disturbance. A native of Elis in the Peloponnese, Pyrrho lived around 365 to 270 B.C. and worked during a period shaped by the dissolution of the classical city-state and the rise of Hellenistic cosmopolitanism. In this context of political instability and cultural diversity, the question of how to achieve happiness (eudaimonia) acquired renewed urgency. Pyrrho’s answer was radical: happiness does not depend on knowing the ultimate truth about things, but on recognizing that such truth is beyond our reach. In his view, things are equally indeterminable, ungraspable, and undecidable (adiaphora, astathmêta, anepíkrita); faced with this situation, the wise course is epoché — suspension of judgment — rather than hasty assertion. His principal disciple, Timon of Phlius, preserved his ideas in verse form, enabling Pyrrhonism to reach later generations. ...

Seneca Lucius Annaeus Seneca was born in Corduba, in Hispania, around 4 BCE, the son of Seneca the Elder, a renowned teacher of rhetoric. He was the most influential — and also the most controversial — of the Roman Stoics: a wealthy and powerful senator, he endured exile in Corsica under the emperor Claudius and, on his return to Rome, became tutor and later advisor to the young Nero, whom he sought to restrain in the early years of his reign. Accused of taking part in the Pisonian conspiracy, he was forced by Nero to take his own life in 65 CE — a death that, according to Tacitus’s account, he faced with the serenity his philosophy preached. ...

Sextus Empiricus Greek physician and philosopher, the principal systematizer of Pyrrhonian skepticism. His works are the most complete source on the ancient skeptical tradition founded by Pyrrho. While the dogmatists (Stoics, Epicureans, Platonists) claimed to reach definitive truth, Sextus defends the suspension of judgment (epoché) as the path to tranquility (ataraxia). His influence was decisive on modern philosophy, especially on Montaigne, Descartes, and Hume. Sextus Empiricus probably lived and wrote between the second and third centuries CE, at a time when Pyrrhonian skepticism had been revived by Aenesidemus roughly two centuries after Pyrrho of Elis. The epithet “Empiricus” signals his affiliation with the Empiric school of medicine, which rejected hidden causal theories and confined itself to observable experience — a methodological stance that directly mirrors his philosophy. Although almost nothing is known of his biography, his textual output is exceptional: the Outlines of Pyrrhonism offers a pedagogical presentation of the skeptical method in three books, while the eleven books of Adversus Mathematicos systematically dismantle the knowledge-claims of grammarians, rhetoricians, geometers, arithmeticians, astrologers, musicians, logicians, natural philosophers, and ethicists. This breadth shows that Sextus’s skepticism was not intellectual nihilism, but a rigorous philosophical program: by demonstrating that for every dogmatic assertion there is a counter-argument of equal force (isostheneia), he aims to induce suspension of judgment and, as a consequence, peace of mind. ...

Zeno of Citium Founder of Stoicism. He taught at the Stoa Poikilê (Painted Porch) in Athens — hence the name of the school. After hearing the story of Socrates through the cynicism of Crates, he abandoned commerce to dedicate himself to philosophy. He taught that virtue is the only real good; everything else (wealth, health, fame) is indifferent (adiaphora). The universe is permeated by the divine Logos (rational fire) and each event occurs by rational necessity. ...