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Ancient Skepticism (Pyrrho to Sextus Empiricus)
c. 300 BC – AD 200· School or movement· Knowledge, logic & science
Mostly agreedGood evidence; some details uncertain.
Greek schools that argued no claim can be known for certain, so the wise person suspends judgment and finds peace.
See it on the Philosophy map →The idea
The idea: for every argument there is an equally strong counter-argument, so suspend judgment (epochē). The reasoning, set out in standard 'modes': honey tastes sweet to the healthy and bitter to the sick; a square tower looks round from afar. Which appearance is true? Pyrrho of Elis, who travelled to India with Alexander, taught this as a path to calm; Arcesilaus and Carneades made Plato's Academy skeptical. The main objection: 'nothing can be known' undercuts itself, and a total skeptic could not act.
Why it matters
It set the challenge every later theory of knowledge must answer; its rediscovery in the 1560s fuelled Montaigne, Descartes and the modern demand for evidence.
Where it comes from
Pyrrho wrote nothing. Our main source is Sextus Empiricus's Outlines of Pyrrhonism (c. AD 200), plus Cicero's Academica and Diogenes Laertius.
Still debated
Whether Pyrrho's ideas came partly from Indian sages he met, and how radical his own skepticism really was, are still debated.
Connections (4)
▸Plato led, via the Academy, to one branch of Ancient Skepticism (Pyrrho to Sextus Empiricus)Mostly agreed
The connection
Plato's dialogues often end without answers, and his Socrates claims to know nothing. Around 266 BC Arcesilaus, the Academy's new head, made that side of Plato central: argue both sides, assert nothing. For two centuries Plato's own school was the leading skeptical school, attacking Stoic claims to certainty. Pyrrhonism grew separately, from Pyrrho.
When and how
Athens, about 266–90 BC, under Academy heads Arcesilaus and Carneades; Aenesidemus later left the Academy to revive Pyrrho's stricter skepticism.
How sure are we?
Cicero, who studied with Academic skeptics, describes the lineage in his Academica; Sextus Empiricus carefully distinguishes the Academics from the Pyrrhonists.
Debates and open questions
Was Arcesilaus faithful to Plato, who clearly believed in Forms, or did he redirect the school? Ancient and modern readers disagree.
▸Ancient Skepticism (Pyrrho to Sextus Empiricus) inspired Michel de Montaigne, EssaysWell documented
The connection
Montaigne read the Outlines of Pyrrhonism by Sextus Empiricus, newly printed in Latin, and adopted its method: set opposing arguments against each other until judgment is suspended. His longest essay, the 'Apology for Raymond Sebond', uses it to deflate human reason, and he had skeptical sayings painted on his library beams.
When and how
Montaigne's tower library near Bordeaux, mid-1570s; he used Henri Estienne's 1562 Latin translation of Sextus, and in 1576 had a medal struck bearing scales and the Greek word epecho, 'I suspend judgment'
How we know
The 'Apology' quotes Sextus repeatedly, and several beam inscriptions, still visible, come from Sextus.
Debates and open questions
Whether Montaigne was a true Pyrrhonist or used doubt to make room for faith, a position called fideism, is still argued.
▸Ancient Skepticism (Pyrrho to Sextus Empiricus) suspended judgement on What can we know?Mostly agreed
The connection
The Skeptics gave the most radical answer: perhaps nothing. Arguing both sides of every question, they showed that appearances conflict and that any proof needs a further proof, without end. Rather than claim nothing can be known, itself a claim, Pyrrhonists suspended judgment and lived by appearances and custom.
When and how
Greece and Rome, c. 300 BC – AD 200: Pyrrho, Arcesilaus, Carneades, Aenesidemus and Sextus Empiricus, whose Outlines of Pyrrhonism survives.
How sure are we?
Sextus's works set out the arguments in detail, including Agrippa's five modes, whose regress of justification is still discussed today.
Debates and open questions
Whether anyone can truly live without beliefs, and whether modern replies to the regress, such as foundationalism or coherentism, actually defeat it.
▸Ancient Skepticism (Pyrrho to Sextus Empiricus) was answered by René DescartesMostly agreed
The connection
Ancient Skeptic arguments, revived in print in the 1560s, threatened all certainty: the senses deceive and dreams feel real. Descartes turned their method into a tool, doubting everything on purpose to find what could not be doubted, the cogito, then rebuilding knowledge on it as his answer to the skeptics.
When and how
Henri Estienne printed Sextus Empiricus in Latin in 1562; Descartes answered in the Meditations, published in Paris in 1641.
How sure are we?
The First Meditation uses classic skeptical arguments, and Descartes' replies discuss skeptics directly; historian Richard Popkin documented this 'skeptical crisis' of the period.
Debates and open questions
Many think Descartes failed to beat the skeptics, since his road back from doubt depends on proving God; whether he ever truly doubted is also debated.