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Philo of Alexandria Note on dating: Philo’s dates are not known with precision; his life is estimated between c. 25/15 BCE and c. 45/50 CE, with the firmly dated embassy he led to Caligula in 39/40 CE — recounted in Legatio ad Gaium — serving as the principal point of reference. Philo of Alexandria — in Latin Philo Iudaeus, “Philo the Jew” — was a Hellenistic Jewish thinker from one of the wealthiest and most influential families of the Jewish diaspora in Alexandria. A Roman citizen, a contemporary of Jesus, Seneca, and the early Julio-Claudian emperors, he wrote entirely in Greek and stood at the crossroads of two traditions: biblical Judaism and Greek philosophy — especially Middle Platonism, Stoicism, and Pythagoreanism. In 38 CE Alexandria was the scene of violent anti-Jewish attacks under the governor Aulus Avillius Flaccus (narrated in In Flaccum), and in 39/40 CE Philo led the delegation of Alexandrian Jews that travelled to Rome to lay their grievances before Caligula. A caveat: Philo is often imprecisely labelled “Neoplatonist.” Strictly speaking, he is pre-Neoplatonist — earlier than Plotinus by more than two centuries — and is best situated within Middle Platonism. ...

Pico della Mirandola Giovanni Pico della Mirandola. Italian prodigy philosopher; knew Latin, Greek, Hebrew, Arabic, and Aramaic. Proposed to hold a debate in Rome with 900 theses from all philosophical traditions — Pope Innocent VIII condemned some of them. Died at age 31. Trained at the Platonic Academy of Florence in close dialogue with Marsilio Ficino and within the circle of Lorenzo de’ Medici, Pico represented the apex of Renaissance humanism. In 1486, he composed the 900 Conclusions — theses drawn from sources as diverse as Plato, Aristotle, Avicenna, Averroes, Jewish Kabbalah, and the Corpus Hermeticum — with the ambition of demonstrating that philosophical and religious truth was one, accessible through multiple paths. The project was cut short when a papal commission condemned thirteen of the theses as heretical; Pico fled to France and only returned to Italy under the protection of Lorenzo de’ Medici. ...

Plato Student of Socrates and the most influential philosopher of antiquity, Plato was born into an aristocratic Athenian family around 428 BCE. His master’s execution in 399 BCE marked him deeply and turned him away from the political career his lineage had reserved for him. After years of travel — which tradition links to contact with the Pythagoreans of southern Italy and to his failed attempts to educate the tyrants of Syracuse — he founded the Academy around 387 BCE, the first institution of higher learning in the West, which would endure for more than nine centuries. His work has reached us almost intact, almost entirely in the form of dialogues, with Socrates as the central character. ...

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. ...

Porphyry Porphyry of Tyre — in Greek Porphýrios, a name adopted in place of his Semitic birth name Malchus (“king” in Phoenician) — was born around 234 CE in Tyre (on the coast of present-day Lebanon) and died around 305 CE. A caveat: he should not be confused with Porphyry of Gaza (5th century), a Christian bishop with the same name, nor with other late-antique figures bearing it. After studying in Athens with Cassius Longinus, in around 263 CE he joined the circle of Plotinus in Rome, of whom he became the most celebrated pupil. He served as editor of the Enneads (posthumously published c. 301), arranging the master’s writings into six groups of nine treatises and prefacing them with the Vita Plotini (Life of Plotinus) — a fundamental biographical source on Plotinus. His influence, however, reaches far beyond his editorial work: through the Isagoge, Porphyry shaped the entry of Aristotelian logic into the medieval world. ...

Proclus Proclus Lycaeus Diadochus (in Greek Próklos Lýkios Diádokhos, “Proclus the Lycian, the Successor”) was born in Constantinople in 412 CE and died in Athens on 17 April 485 CE. A caveat: he should not be confused with Proclus Procopius (an orator of the 5th century) or other homonymous late-antique figures. The son of a wealthy family from Lycia (in the south of present-day Turkey), he was educated in Alexandria and soon moved to Athens, where he studied with Plutarch of Athens (not to be confused with the essayist of Chaeronea) and with Syrianus, whom he succeeded as head of the Academy — hence his title Diádokhos, “the Successor.” He was the last great systematizer of pagan Neoplatonism before the closure of the Academy by Emperor Justinian in 529 CE. His work organizes the Plotinian inheritance into a rigorous network of propositions and triads, in a project comparable, in ambition, to Aquinas’s Summa — but in an entirely pagan key. ...

Protagoras Born in Abdera around 490 BCE, Protagoras was the first and most famous of the Sophists — the itinerant teachers who, for a fee, taught the young the rhetoric and aretê (excellence) needed for success in the public life of the Greek cities. He frequented the circle of Pericles in Athens and even drew up the laws for the colony of Thurii. He is the figure who best embodies the spirit of the sophistic movement. ...

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. ...

Pythagoras Born on the island of Samos around 570 BCE, Pythagoras emigrated to Croton, in southern Italy (Magna Graecia), where he founded a philosophical-religious community famous for its austere way of life, its rules of silence, and the secrecy of its teachings. Since he wrote nothing and his disciples attributed everything to the master, it is difficult to separate his ideas from those of the Pythagoreans who followed him; already in antiquity his figure blended with legend. ...

René Descartes Often called the “father of modern philosophy,” René Descartes was born in 1596 in La Haye, in the French region of Touraine, and was educated at the rigorous Jesuit college of La Flèche. Dissatisfied with bookish learning, he enlisted as a volunteer in the armies of the Thirty Years’ War; it was during this period, by his own account, that in 1619 he glimpsed a universal method capable of giving philosophy the same certainty as mathematics. He spent most of his productive life in the Dutch Republic and died in 1650 in Stockholm, where he had been invited to tutor Queen Christina of Sweden. He was also a great mathematician: analytic geometry and the coordinate system that bears his name are his creations. ...

Richard Rorty Richard McKay Rorty was an American philosopher who taught at Princeton, the University of Virginia, and Stanford. He began as an analytic philosopher formed in the Wittgenstein-Sellars tradition, but Philosophy and the Mirror of Nature (1979) projected him as one of the most radical critics of the Western epistemological tradition. Rorty is the principal representative of neopragmatism, which combines the American pragmatist heritage (Dewey, James) with elements of continental philosophy (Heidegger, Derrida) and late analytic philosophy (Wittgenstein, Quine, Sellars). ...

Robert Nozick Robert Nozick was an American political philosopher and professor at Harvard, whose Anarchy, State, and Utopia (1974) became the most systematic and rigorous libertarian response to John Rawls’s theory of justice, reorienting anglophone political-philosophical debate for decades. Beyond political philosophy, he made original contributions to epistemology, metaphysics, and ethics. Key Concepts Rights as Side Constraints (Anarchy, State, and Utopia, 1974): Nozick holds that individual rights are side constraints on action — not factors to be maximised within a calculation, but limits that cannot be violated even when violation would produce better outcomes for the greatest number. Individual dignity prohibits using persons as mere means to others’ ends. ...

Rodolfo Kusch Born in Buenos Aires in 1922, into a family of German origin, Rodolfo Kusch united philosophy and anthropology in a rare way: instead of thinking America from European books, he traveled through northwestern Argentina and the Bolivian highlands in extensive fieldwork, listening to Quechua and Aymara thought. From this experience arose a radical question: is European ontology really capable of comprehending the greater part of human experience? His answer turns on a distinction that Spanish — and Portuguese — allow with singular clarity: that between being (ser) and dwelling (estar). “Being” expresses the modern Western mode: to be something, to produce, to assert oneself, to project oneself. “Dwelling” expresses another way of inhabiting the world: to be here, rooted in the land, in the community, in the here-and-now — the mode proper to the human being of deep America. For Kusch these are two distinct and irreducible ontologies. ...

Roland Barthes Roland Barthes (12 November 1915, Cherbourg — 26 March 1980, Paris) was a French literary critic, semiologist, and essayist, one of the central figures of structuralism and of the post-structuralist turn. Marked in youth by tuberculosis, which kept him from a regular academic career, he built an unclassifiable body of work poised between criticism, philosophy, and literature. In 1977 he was elected to a chair of literary semiology at the Collège de France. He died in 1980, weeks after being struck by a van in Paris. ...

Ronald Dworkin American legal and moral philosopher, professor at Yale, Oxford, and New York University; Dworkin’s work constitutes the most influential critique of legal positivism in the 20th century and a comprehensive normative theory integrating law, political morality, and ethics. Key Concepts Principles vs. rules: against Hart, Dworkin argues that legal systems include not only rules (which apply in an all-or-nothing fashion) but also principles and policies. Principles such as “no one may profit from his own wrong” have weight and dimension; they do not derive from any rule of recognition — which shows that positivism is an insufficient descriptive theory of law Critique of discretion: Hart concedes that in “hard cases” judges exercise discretion, thereby creating new law. Dworkin rejects this: even in hard cases there is a right answer (the one right answer thesis) — the judge discovers existing law rather than creating it Rights as trumps: in Taking Rights Seriously (1977), individual rights are “trumps” that override arguments of collective utility or policy — no social goal can justify violating them. Dworkin defends an egalitarian liberalism grounded in equal concern and respect Law as integrity: in Law’s Empire (1986), law is neither a collection of brute facts (positivism) nor a list of natural values (natural law theory) but an interpretive practice. Law as integrity requires judges to treat the legal system as expressing a coherent set of moral principles Chain novel (chain novel): a metaphor for the interpretive process — the judge deciding a hard case is like a writer continuing a novel by many authors; he must be faithful to earlier chapters while making the work as good as it can be Judge Hercules: an ideal (not real) figure endowed with superhuman capacity to find the decision that best fits the system’s principles and renders it morally most coherent. The implicit normative claim: actual judicial decisions should approximate this ideal Equality of resources: in Sovereign Virtue (2000), just distribution requires that resources be divided so that no one envies another’s share, correcting disadvantages imposed by brute luck (illness, disability) while respecting personal choices Unity of value: in Justice for Hedgehogs (2011) — the title evoking Isaiah Berlin’s hedgehog that knows “one big thing” — Dworkin argues that ethical and moral values form a coherent system: living well and treating others justly are not competing demands but mutually dependent ones Religion without God: Religion without God (2013, posthumous) extends the unity-of-value thesis to a secular religious attitude that recognises intrinsic value and beauty in the universe without presupposing a personal God Influenced by H.L.A. Hart — the positivism Dworkin critiques in depth Lon Fuller — “inner morality of law” and the integrative function of principles John Rawls — egalitarian liberalism, debates on equality Isaiah Berlin, Kant, and the American liberal tradition Influenced The whole of contemporary legal philosophy (mandatory point of reference) Carlos Nino, Robert Alexy, and debates on the balancing of principles American and European constitutional adjudication Debates on judicial review and constitutional interpretation Works Taking Rights Seriously (1977); A Matter of Principle (1985); Law’s Empire (1986); Life’s Dominion (1993); Freedom’s Law (1996); Sovereign Virtue (2000); Justice in Robes (2006); Is Democracy Possible Here? (2006); Justice for Hedgehogs (2011); Religion without God (2013, posthumous). ...

Rudolf Carnap Rudolf Carnap was the most systematic and influential figure of the Vienna Circle and of logical empiricism, a movement that sought to refound philosophy on the rigor of modern logic and fidelity to experience. Trained in physics, logic, and philosophy in Germany, he studied with Gottlob Frege at Jena before joining the Vienna Circle in the 1920s. With the rise of Nazism he emigrated to the United States, where he taught at Chicago and at the University of California, Los Angeles. His work spans the logical construction of knowledge, the syntax and semantics of language, the theory of confirmation, and inductive logic, always guided by the ideal of conceptual clarity. ...

Saint Augustine Aurelius Augustine was born in 354 in Thagaste, in Roman North Africa, the son of a Christian mother (Monica) and a pagan father. A teacher of rhetoric in Carthage, Rome, and Milan, he traveled a long intellectual and spiritual road: he was kindled to philosophy by reading Cicero, adhered for years to Manichaeism, passed through skepticism, and found in the Neoplatonism of Plotinus the instrument that would lead him back toward Christianity. His conversion in Milan (386) — the famous “tolle, lege” (“take up and read”) scene narrated in the Confessions — was a turning point. He became bishop of Hippo and, until his death in 430, during the Vandal siege, was the greatest thinker of the Patristic age and one of the most influential figures in the whole history of the West. ...

Saul Kripke Saul Aaron Kripke was arguably the most technically gifted analytic philosopher of his generation. Born in Omaha, Nebraska, he showed extraordinary aptitude from adolescence: he published his first mature logical article — a completeness proof for modal logic — at eighteen, and corresponded with professional logicians while still in high school. A professor at Princeton and later at the CUNY Graduate Center, Kripke transformed metaphysics, philosophy of language, and modal logic to such a degree that virtually all analytic philosophy after the debates surrounding Naming and Necessity is, in some sense, a response to him. ...

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. ...