Skepticism

1. Pyrrho begins teaching skeptical practice at Elis

   Jan 1, 330 BCELabels: Pyrrho of, Elis, Epoch

   In the late 4th century BCE, Pyrrho of Elis became known for a way of life built around epochē (suspension of judgment). Ancient reports describe him as arguing that equally strong reasons can often be given on both sides of a question, so we should avoid firm claims about how things really are. This set the pattern for later Pyrrhonian skepticism, which treated doubt as a practical discipline as well as a theory about knowledge.

   • Britannica
   • WHE

2. Timon of Phlius preserves Pyrrho’s reputation

   Jan 1, 300 BCELabels: Timon of, Pyrrhonism, Literary works

   Pyrrho left no surviving writings, so later knowledge of his skepticism depended heavily on followers. Timon of Phlius, his student, helped shape the early Pyrrhonian tradition through literary works that portrayed Pyrrho as a model of calm and non-assertion. This mattered because Pyrrhonism was transmitted more as a style of inquiry and living than as a fixed set of doctrines.

   • Britannica
   • SEP Skepticism

3. Arcesilaus turns Plato’s Academy toward skepticism

   Jan 1, 265 BCELabels: Arcesilaus, Plato's Academy, Academic skepticism

   Arcesilaus, who led Plato’s Academy in the early 3rd century BCE, launched the school’s skeptical phase (often called Academic skepticism). He challenged the Stoic idea that there is a special type of perception that guarantees truth, and urged caution about giving assent to philosophical claims. This created a major skeptical rival to Pyrrhonism inside an influential institutional setting: the Academy itself.

   • SEP Arcesilaus
   • Britannica Skepticism

4. Carneades strengthens Academic arguments and probabilism

   Jan 1, 167 BCELabels: Carneades, Academic skepticism, Probabilism

   In the 2nd century BCE, Carneades became the most famous head of the skeptical Academy and pushed skepticism to a high point. He argued forcefully that certain knowledge is not available, but also developed a practical approach: people can guide action by what seems more plausible rather than by certainty. This made skepticism less like paralysis and more like a disciplined approach to decision-making under uncertainty.

   • Britannica
   • REP summary

5. Carneades’ Rome lectures publicize skeptical method

   Jan 1, 155 BCELabels: Carneades, Rome, Athenian embassy

   In 155 BCE, Carneades visited Rome as part of an Athenian embassy and gave paired speeches arguing for and against justice. The display showed a key skeptical technique: matching arguments on both sides to weaken dogmatic confidence. This episode helped introduce Roman audiences to Greek philosophical debate and made skepticism a visible cultural force beyond Athens.

   • Britannica
   • REP summary

6. Aenesidemus revives Pyrrhonism against the late Academy

   Jan 1, 50 BCELabels: Aenesidemus, Pyrrhonism, Late Academy

   In the 1st century BCE, Aenesidemus argued that the Academy had drifted into its own kind of dogmatism and called for a return to Pyrrhonian suspension of judgment. He wrote works (now mostly lost) that helped restart Pyrrhonism as a distinct movement. This revival mattered because it re-centered skepticism on inquiry without settling conclusions, rather than on any fixed skeptical “theory.”

   • Cambridge Core
   • SEP Skepticism

7. Cicero’s Academica transmits Academic skepticism in Latin

   May 1, 45 BCELabels: Cicero, Academica, Latin transmission

   In 45 BCE, Cicero wrote the Academica, a dialogue explaining debates about knowledge, assent, and uncertainty within the Hellenistic Academy. Because many Greek skeptical writings were later lost, Cicero’s Latin work became a crucial bridge for later readers. It helped keep skeptical arguments alive for later antiquity and, much later, early modern Europe.

   • Philopedia
   • Attalus

8. Agrippa’s Five Modes become classic skeptical tools

   Jan 1, 100Labels: Agrippa, Five Modes, Skeptical toolkit

   By around the 1st–2nd century CE, later skeptics credited Agrippa with five influential “modes” (argument patterns) that push thinkers toward suspension of judgment. These include arguments from deep disagreement, infinite regress of justification, and relativity of appearances. The Five Modes became a compact, teachable toolkit for skeptical criticism of claims to certain knowledge.

   • SEP Skepticism

9. Sextus Empiricus systematizes Pyrrhonian skepticism

   Jan 1, 200Labels: Sextus Empiricus, Pyrrhonism, Outlines

   Sextus Empiricus, probably active in the 2nd or 3rd century CE, wrote the most complete surviving presentation of Pyrrhonism. In works including Outlines of Pyrrhonism, he explains how skeptics set opposing arguments against each other to reach epochē, aiming at ataraxia (tranquility). Because his writings survived, Sextus became the main gateway through which later periods learned Pyrrhonian methods.

   • SEP Sextus
   • SEP Skepticism

10. Henri Estienne publishes Latin Sextus, spreading Pyrrhonism

    Jan 1, 1562Labels: Henri Estienne, Latin Sextus, Printing

    In 1562, Henri Estienne (Henricus Stephanus) printed an influential Latin translation of Sextus Empiricus’ Outlines. Making Sextus widely readable in Latin reshaped Renaissance debates about certainty, faith, and the limits of reason. This publication helped move ancient Pyrrhonian arguments into early modern philosophy.

    • IEP Renaissance
    • Eton catalogue

11. Montaigne’s Essays popularize a skeptical stance in Europe

    Jan 1, 1580Labels: Michel de, Essays, Sebond

    In 1580, Michel de Montaigne published the first edition of his Essays, which include sustained skeptical themes (especially in the “Apology for Raymond Sebond”). Drawing on revived ancient skepticism, Montaigne used doubt to criticize intellectual arrogance and to encourage modesty about human reason. His accessible style helped skepticism reach a broad educated audience beyond specialist philosophy.

    • IEP Renaissance
    • Philopedia Montaigne

12. Bayle’s Dictionary amplifies skeptical critique and debate

    Jan 1, 1697Labels: Pierre Bayle, Historical and, Critical notes

    In 1697, Pierre Bayle published the first edition of his Historical and Critical Dictionary, famous for careful argument and extensive critical notes. Bayle used skeptical scrutiny to expose contradictions and weak reasoning in many philosophical and theological claims, shaping Enlightenment debates. Even when readers disagreed with him, his method made rigorous doubt a central intellectual habit.

    • IEP Bayle

13. Hume’s Treatise re-frames skepticism within empiricism

    Jan 1, 1739Labels: David Hume, Treatise, Empiricism

    In 1739–1740, David Hume published A Treatise of Human Nature, developing a powerful empiricist account of how beliefs form and why certainty is hard to justify. Hume’s work renewed skeptical pressure on ideas like necessary causation and a stable self, while also treating skepticism as something the mind must manage in ordinary life. This helped define skepticism as a lasting problem for modern epistemology, not just an ancient school.

    • Britannica Treatise
    • Treatise info

14. Moore’s “Proof of an External World” marks a modern pushback

    Jan 1, 1939Labels: G E, Proof of, Common sense

    In 1939, G. E. Moore presented his famous “here is one hand” argument to defend common-sense knowledge of the external world against radical skepticism. The argument did not end skeptical debate, but it became a landmark example of a different strategy: starting from everyday knowledge claims rather than skeptical hypotheses. By the 20th century, skepticism had become a stable reference point—something major philosophers routinely addressed, not a single school with one set of doctrines.

    • IEP Moore
    • Here one hand