Skepticism

Introduction
Senses and applications
Ancient skepticism
Medieval skepticism
Modern skepticism
- The Reformation
- The 17th century
- The 18th century
- Skepticism from the 19th century to the present
  - Existentialism
  - Idealism and naturalism
  - Logical positivism and linguistic philosophy
  - Moore and Wittgenstein
  - Postmodernism
Criticism and evaluation

References & Edit History Quick Facts & Related Topics

Images

Fragment of a Roman fresco showing Socrates seated and draped in a white robe, with Greek text above, on a red background with visible cracks.

Marble bust of Marcus Tullius Cicero, shown with short hair and draped clothing, displayed against a black background.

Heinrich Cornelius Agrippa von Nettesheim

Engraving of Pierre-Daniel Huet by Gerard Edelinck after Nicolas de Largilliere, showing a man with curly hair, clerical robes, and a cross, set in an oval frame.

Christian Kierkegaard: Søren Kierkegaard

At a Glance

skepticism summary

Related Questions

How can a distant round-looking tower illustrate a skeptical argument about perception?
How did Academic skepticism challenge Stoicism and Epicureanism?
How did Aenesidemus’s 10 tropes challenge trust in sense perception?
How did Carneades respond to the claim that Academic skepticism is self-contradictory?
How did Descartes use clear and distinct ideas as a criterion of truth?
How did Heraclitus’s idea of constant change support skeptical thinking?
How did Hume think habit and custom shape beliefs about the world?
How did Martin Luther differ from Erasmus about the possibility of certain religious knowledge?
How did Montaigne and Francisco Sanches use skepticism to question knowledge claims?
How did Pierre Bayle use skeptical arguments against philosophical and theological systems?
How did Protagoras’s claim that “man is the measure of all things” encourage relativism?
How did Pyrrhonism differ from Academic skepticism?
How did Pyrrhonists believe people could live without making firm knowledge claims?
How did René Descartes use systematic doubt in his search for certainty?
How did Sextus Empiricus challenge dogmatic philosophers?
How did ancient skepticism challenge claims of certain medical knowledge?
How did skepticism first develop in ancient Greece?
How did skepticism influence the development of epistemology?
How did skepticism question whether moral values have an objective basis?
How did the rediscovery of Sextus Empiricus’s writings influence Renaissance and early modern philosophy?
How does the brain-in-a-vat thought experiment raise doubts about sense experience?
What argument did Gorgias make about existence knowledge and communication?
What is the problem of the criterion in skeptical philosophy?
What were the tropes used by Pyrrhonian skeptics?
Which books by Sextus Empiricus describe Pyrrhonian skepticism?
Why can attempts to justify a standard of truth lead to an infinite regress?
Why did Academic skeptics argue that certainty was impossible?
Why did Academic skeptics use probability when making decisions?
Why did Descartes consider “I think therefore I am” indubitable?
Why did Kant argue that people cannot know things-in-themselves?
Why did Socrates say that he knew nothing?
Why did critics argue that Descartes had not defeated skepticism?
Why have critics argued that skepticism is self-refuting?
Why is using a criterion to justify itself considered circular reasoning?
What are some general characteristics of postmodernism?
What do postmodernists believe?
How is postmodernism related to relativism?
Where did Marxism come from?
Why is Marxism important?
How is Marxism different from other forms of socialism?
How does Marxism differ from Leninism?

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External Websites

Rebus Community - Skepticism
Humanities LibreTexts - Skepticism
Florida State College at Jacksonville Pressbooks - Skepticism
International Journal of Humanities and Social Science Studies - Skepticism and its Various Forms (PDF)
Internet Encyclopedia of Philosophy - Ancient Greek Skepticism
Stanford Encyclopedia of Philosophy - Skepticism

David Hume Scottish philosopher David Hume, oil on canvas by Allan Ramsay, 1766; in the Scottish National Portrait Gallery, Edinburgh.

Skepticism

philosophy

Also known as: scepticism

Written by

Richard H. Popkin

Emeritus Professor of Philosophy, Washington University, St. Louis, Missouri. Adjunct Professor of History and Philosophy, University of California, Los Angeles. Author of History of Scepticism from...

Richard H. Popkin

Fact-checked by

Britannica Editors

Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....

Britannica Editors

Last updated

Nov. 4, 2026 •History

In Western philosophy, skepticism is the attitude of doubting knowledge claims set forth in various areas. Skeptics have challenged the adequacy or reliability of these claims by asking what principles they are based upon or what they actually establish. They have questioned whether some such claims really are, as alleged, indubitable or necessarily true, and they have challenged the purported rational grounds of accepted assumptions. In everyday life, practically everyone is skeptical about some knowledge...

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