Skepticism, also spelled scepticism, is a questioning attitude or doubt toward knowledge claims that are seen as mere belief or dogma. For example, if a person is skeptical about claims made by their government about an ongoing war then the person doubts that these claims are accurate. In such cases, skeptics normally recommend not disbelief but suspension of belief, i.e. maintaining a neutral attitude that neither affirms nor denies the claim. This attitude is often motivated by the impression that the available evidence is insufficient to support the claim. Formally, skepticism is a topic of interest in philosophy, particularly epistemology. More informally, skepticism as an expression of questioning or doubt can be applied to any topic, such as politics, religion, or pseudoscience. It is often applied within restricted domains, such as morality (moral skepticism), atheism (skepticism about the existence of God), or the supernatural. Some theorists distinguish "good" or moderate skepticism, which seeks strong evidence before accepting a position, from "bad" or radical skepticism, which wants to suspend judgment indefinitely.
Philosophical skepticism is one important form of skepticism. It rejects knowledge claims that seem certain from the perspective of common sense. Radical forms of philosophical skepticism deny that "knowledge or rational belief is possible" and urge us to suspend judgment on many or all controversial matters. More moderate forms claim only that nothing can be known with certainty, or that we can know little or nothing about nonempirical matters, such as whether God exists, whether human beings have free will, or whether there is an afterlife. In ancient philosophy, skepticism was understood as a way of life associated with inner peace.
Skepticism has been responsible for many important developments in science and philosophy. It has also inspired several contemporary social movements. Religious skepticism advocates for doubt concerning basic religious principles, such as immortality, providence, and revelation. Scientific skepticism advocates for testing beliefs for reliability, by subjecting them to systematic investigation using the scientific method, to discover empirical evidence for them.
Definition and semantic field
Skepticism, also spelled scepticism, (from the Greek 'σκέπτομαι' skeptomai, to search, to think about or look for) refers to a doubtful attitude toward knowledge claims. So if a person is skeptical of their government's claims about an ongoing war then the person has doubts that these claims are true. Or being skeptical that one's favorite hockey team will win the championship means that one is uncertain about the strength of their performance. Skepticism about a claim implies that one does not believe this claim to be true. But it does not automatically follow that one should believe that the claim is false either. Instead, skeptics usually recommend a neutral attitude: beliefs about this matter should be suspended. In this regard, skepticism about a claim can be defined as the thesis that "the only justified attitude with respect to [this claim] is suspension of judgment". It is often motivated by the impression that one cannot be certain about it. This is especially relevant when there is significant expert disagreement. Skepticism is usually restricted to a claim or a field of inquiry. So religious and moral skeptics have a doubtful attitude about religious and moral doctrines. But some forms of philosophical skepticism, are wider in that they reject any form of knowledge.
Some definitions, often inspired by ancient philosophy, see skepticism not just as an attitude but as a way of life. This is based on the idea that maintaining the skeptical attitude of doubt toward most concerns in life is somehow superior compared to living in dogmatic certainty, for example, because such a skeptic person has more happiness and peace of mind or because it is morally better. In contemporary philosophy, on the other hand, skepticism is often understood neither as an attitude nor as a way of life but as a thesis: the thesis that knowledge does not exist.
Skepticism is related to various terms. It is sometimes equated with agnosticism and relativism. However, there are slight differences in meaning. Agnosticism is often understood more narrowly as skepticism about religious questions, in particular, about the Christian doctrine. Relativism does not deny the existence of knowledge or truth but holds that they are relative to a person and differ from person to person, for example, because they follow different cognitive norms. The opposite of skepticism is dogmatism, which implies an attitude of certainty in the form of an unquestioning belief. A similar contrast is often drawn in relation to blind faith and credulity.
Various types of skepticism have been discussed in the academic literature. Skepticism is usually restricted to knowledge claims on one particular subject, which is why its different forms can be distinguished based on the subject. For example, religious skeptics distrust religious doctrines and moral skeptics raise doubts about accepting various moral requirements and customs. Skepticism can also be applied to knowledge in general. However, this attitude is usually only found in some forms of philosophical skepticism. A closely related classification distinguishes based on the source of knowledge, such as skepticism about perception, memory, or intuition. A further distinction is based on the degree of the skeptical attitude. The strongest forms assert that there is no knowledge at all or that it is impossible. Weaker forms merely state that one can never be absolutely certain.
Some theorists distinguish between a good or healthy form of moderate skepticism in contrast to a bad or unhealthy form of radical skepticism. On this view, the "good" skeptic is a critically-minded person who seeks strong evidence before accepting a position. The "bad" skeptic, on the other hand, wants to "suspend judgment indefinitely ... even in the face of demonstrable truth". Another categorization focuses on the motivation for the skeptical attitude. Some skeptics have ideological motives: they want to replace inferior beliefs with better ones. Others have a more practical outlook in that they see problematic beliefs as the cause of harmful customs they wish to stop. Some skeptics have very particular goals in mind, such as bringing down a certain institution associated with the spread of claims they reject.
Philosophical skepticism is a prominent form of skepticism and can be contrasted with non-philosophical or ordinary skepticism. Ordinary skepticism involves a doubting attitude toward knowledge claims that are rejected by many. Almost everyone shows some form of ordinary skepticism, for example, by doubting the knowledge claims made by flat earthers or astrologers. Philosophical skepticism, on the other hand, is a much more radical and rare position. It includes the rejection of knowledge claims that seem certain from the perspective of common sense. Some forms of it even deny that one knows that "I have two hands" or that "the sun will come out tomorrow". It is taken seriously in philosophy nonetheless since it has proven very hard to conclusively refute philosophical skepticism.
In various fields
Skepticism has been responsible for important developments in various fields, such as science, medicine, and philosophy. In science, the skeptical attitude toward traditional opinions was a key factor in the development of the scientific method. It emphasizes the need to scrutinize knowledge claims by testing them through experimentation and precise measurement. In the field of medicine, skepticism has helped the establishment of more advanced forms of treatment by putting into doubt traditional forms based on intuitive appeal rather than empirical evidence. In the history of philosophy, skepticism has often played a productive role not just for skeptics but also for non-skeptical philosophers. This is due to its critical attitude that continues to challenge the epistemological foundations of a great variety of philosophical theories. This challenge can help to keep speculation in check and may provoke creative responses transforming the theory in question in order to overcome the problems posed by skepticism. According to Richard H. Popkin, "the history of philosophy can be seen, in part, as a struggle with skepticism". In this regard, it has led many contemporary philosophers to abandon the quest for absolutely certain or indubitable first principles of philosophy, which was still prevalent in many earlier periods. Skepticism has been an important topic throughout the history of philosophy and is still a widely discussed subject today.
As a philosophical school or movement, skepticism arose both in ancient Greece and India. In India the Ajñana school of philosophy espoused skepticism. It was a major early rival of Buddhism and Jainism, and a possibly major influence on Buddhism. Two of the foremost disciples of the Buddha, Sariputta and Moggallāna, were initially the students of the Ajñana philosopher Sanjaya Belatthiputta, and a strong element of skepticism is found in Early Buddhism, most particularly in the Aṭṭhakavagga sutra, but it is inconclusive the total effect these philosophies had on each other. Since skepticism is a philosophical attitude and a style of philosophizing rather than a position, the Ajñanins may have influenced other skeptical thinkers of India such as Nagarjuna, Jayarāśi Bhaṭṭa, and Shriharsha.
In Greece philosophers as early as Xenophanes (c. 570 – c. 475 BCE) expressed skeptical views, as did Democritus and a number of Sophists. Gorgias, for example, reputedly argued that nothing exists, that even if there were something we could not know it, and that even if we could know it we could not communicate it. The Heraclitean philosopher Cratylus refused to discuss anything and would merely wriggle his finger, claiming that communication is impossible since meanings are constantly changing. Socrates also had skeptical tendencies, claiming to know nothing worthwhile.
There were two major schools of skepticism in the ancient Greek and Roman world. The first was Pyrrhonism, founded by Pyrrho of Elis (c. 360–270 BCE). The second was Academic Skepticism, so-called because its two leading defenders, Arcesilaus (c. 315–240 BCE) who initiated the philosophy, and Carneades (c. 217–128 BCE), the philosophy's most famous proponent, were heads of Plato's Academy. Pyrrhonism's aims are psychological. It urges suspension of judgment (epoche) to achieve mental tranquility (ataraxia). The Academic Skeptics denied that knowledge is possible (acatalepsy). The Academic Skeptics claimed that some beliefs are more reasonable or probable than others, whereas Pyrrhonian skeptics argue that equally compelling arguments can be given for or against any disputed view. Nearly all the writings of the ancient skeptics are now lost. Most of what we know about ancient skepticism is from Sextus Empiricus, a Pyrrhonian skeptic who lived in the second or third century CE. His works contain a lucid summary of stock skeptical arguments.
Ancient skepticism faded out during the late Roman Empire, particularly after Augustine (354–430 CE) attacked the skeptics in his work Against the Academics (386 CE). There was little knowledge of, or interest in, ancient skepticism in Christian Europe during the Middle Ages. Interest revived during the Renaissance and Reformation, particularly after the complete writings of Sextus Empiricus were translated into Latin in 1569 and Martin Luther's skepticism of holy orders. A number of Catholic writers, including Francisco Sanches (c. 1550–1623), Michel de Montaigne (1533–1592), Pierre Gassendi (1592–1655), and Marin Mersenne (1588–1648) deployed ancient skeptical arguments to defend moderate forms of skepticism and to argue that faith, rather than reason, must be the primary guide to truth. Similar arguments were offered later (perhaps ironically) by the Protestant thinker Pierre Bayle in his influential Historical and Critical Dictionary (1697–1702).
The growing popularity of skeptical views created an intellectual crisis in seventeenth-century Europe. One major response was offered by the French philosopher and mathematician René Descartes (1596–1650). In his classic work, Meditations of First Philosophy (1641), Descartes sought to refute skepticism, but only after he had formulated the case for skepticism as powerfully as possible. Descartes argued that no matter what radical skeptical possibilities we imagine there are certain truths (e.g., that thinking is occurring, or that I exist) that are absolutely certain. Thus, the ancient skeptics were wrong to claim that knowledge is impossible. Descartes also attempted to refute skeptical doubts about the reliability of our senses, our memory, and other cognitive faculties. To do this, Descartes tried to prove that God exists and that God would not allow us to be systematically deceived about the nature of reality. Many contemporary philosophers question whether this second stage of Descartes's critique of skepticism is successful.
In the eighteenth century a new case for skepticism was offered by the Scottish philosopher David Hume (1711–1776). Hume was an empiricist, claiming that all genuine ideas can be traced back to original impressions of sensation or introspective consciousness. Hume argued that on empiricist grounds there are no sound reasons for belief in God, an enduring self or soul, an external world, causal necessity, objective morality, or inductive reasoning. In fact, he argued that "Philosophy would render us entirely Pyrrhonian, were not Nature too strong for it." As Hume saw it, the real basis of human belief is not reason, but custom or habit. We are hard-wired by nature to trust, say, our memories or inductive reasoning, and no skeptical arguments, however powerful, can dislodge those beliefs. In this way, Hume embraced what he called a "mitigated" skepticism, while rejecting an "excessive" Pyrrhonian skepticism that he saw as both impractical and psychologically impossible.
Hume's skepticism provoked a number of important responses. Hume's Scottish contemporary, Thomas Reid (1710–1796), challenged Hume's strict empiricism and argued that it is rational to accept "common-sense" beliefs such as the basic reliability of our senses, our reason, our memories, and inductive reasoning, even though none of these things can be proved. In Reid's view, such common-sense beliefs are foundational and require no proof in order to be rationally justified. Not long after Hume's death, the great German philosopher Immanuel Kant (1724–1804) argued that human moral awareness makes no sense unless we reject Hume's skeptical conclusions about the existence of God, the soul, free will, and an afterlife. According to Kant, while Hume was right to claim that we cannot strictly know any of these things, our moral experience entitles us to believe in them.
Today, skepticism continues to be a topic of lively debate among philosophers. British philosopher, Julian Baggini, posits that reason is perceived as "an enemy of mystery and ambiguity," but, if used properly can be an effective tool for solving many larger societal issues.
Religious skepticism generally refers to doubting given religious beliefs or claims. Historically, religious skepticism can be traced back to Xenophanes, who doubted many religious claims of his time. For example, a religious skeptic might believe that Jesus existed (see historicity of Jesus) while questioning claims that he was the messiah or performed miracles. Religious skepticism is not the same as atheism or agnosticism, though these often do involve skeptical attitudes toward religion and philosophical theology (for example, towards divine omnipotence). Religious people are generally skeptical about claims of other religions, at least when the two denominations conflict concerning some stated belief. Additionally, they may also be skeptical of the claims made by atheists. The historian Will Durant writes that Plato was "as skeptical of atheism as of any other dogma".
A scientific or empirical skeptic is one who questions beliefs on the basis of scientific understanding and empirical evidence.
Scientific skepticism may discard beliefs pertaining to purported phenomena not subject to reliable observation and thus not systematic or testable empirically. Most scientists, being scientific skeptics, test the reliability of certain kinds of claims by subjecting them to a systematic investigation using some type of the scientific method. As a result, a number of claims are considered as "pseudoscience", if they are found to improperly apply or ignore the fundamental aspects of the scientific method.
Professional skepticism is an important concept in auditing. It requires an auditor to have a "questioning mind", to make a critical assessment of evidence, and to consider the sufficiency of the evidence.
- Critical thinking
- Debunker (one who claims to expose claims as being false)
- Scientific skepticism
- Pseudoskepticism (dogma in the form of skepticism)
- Trivialism (opposite of skepticism)
- List of topics characterized as pseudoscience
- The Skeptic (UK magazine), founded by Wendy M. Grossman, examines secularism and the paranormal
- Committee for Skeptical Inquiry, a non-profit organization to encourage the investigation of paranormal and fringe-science
- Skeptical Inquirer, magazine published by the Committee for Skeptical Inquiry
- The Skeptics Society, a nonprofit organization devoted to resisting the spread of pseudoscience, superstition, and irrational beliefs
- Skeptic (U.S. magazine), magazine of The Skeptics Society
- Skepticality, a biweekly podcast of the US Skeptics Society's Skeptic magazine
- The Skeptic's Dictionary, a collection of essays by Robert Todd Carroll
- Skeptical movement, a movement based on scientific skepticism, a term introduced by Carl Sagan
- Skeptics in the Pub, a social meet-up group
- The Amaz!ng Meeting, an annual conference on science, skepticism, and critical thinking
- Euroscepticism, skepticism and/or opposition towards the European Union and its increasing power
- Popkin, R. H.. "The History of Skepticism from Erasmus to Descartes (rev. ed. 1968); C. L. Stough, Greek Skepticism (1969); M. Burnyeat, ed., The Skeptical Tradition (1983); B. Stroud, The Significance of Philosophical Skepticism (1984)". Encyclopedia2.thefreedictionary.com. http://encyclopedia2.thefreedictionary.com/Skeptikoi.
- "Philosophical views are typically classed as skeptical when they involve advancing some degree of doubt regarding claims that are elsewhere taken for granted." utm.edu
- Greco, John (2008) (in en). The Oxford Handbook of Skepticism. Oxford University Press, US. ISBN 978-0195183214. https://books.google.com/books?id=Ozv0lftrUeEC.
- "Definition of SKEPTICISM". http://www.merriam-webster.com/dictionary/skepticism.
- Popkin, Richard H.. "skepticism" (in en). https://www.britannica.com/topic/skepticism.
- Greco, John (2 September 2009). "Introduction" (in en). The Oxford Handbook of Skepticism (1 ed.). Oxford University Press. pp. 3–7. ISBN 978-0-19-518321-4. https://academic.oup.com/edited-volume/28229/chapter-abstract/213259164.
- "Skepticism". HarperCollins. https://www.ahdictionary.com/word/search.html?q=skepticism&submit.x=58&submit.y=14.
- Comesaña, Juan; Klein, Peter (2019). "Skepticism". Metaphysics Research Lab, Stanford University. https://plato.stanford.edu/entries/skepticism/.
- Blackburn, Simon (1 January 2008). "scepticism" (in en). The Oxford Dictionary of Philosophy. Oxford University Press. ISBN 978-0-19-954143-0. https://www.oxfordreference.com/view/10.1093/acref/9780199541430.001.0001/acref-9780199541430-e-2771.
- Vogt, Katja (2021). "Ancient Skepticism". Metaphysics Research Lab, Stanford University. https://plato.stanford.edu/entries/skepticism-ancient/.
- Reed, Baron (11 December 2018) (in en). Skepticism as a Way of Life. Brill. ISBN 978-90-04-39353-0. https://brill.com/view/book/edcoll/9789004393530/BP000005.xml.
- Newton Flew, Antony Garrard. "agnosticism" (in en). https://www.britannica.com/topic/agnosticism.
- Sankey, Howard (1 March 2012). "Scepticism, relativism and the argument from the criterion" (in en). Studies in History and Philosophy of Science Part A 43 (1): 182–190. doi:10.1016/j.shpsa.2011.12.026. ISSN 0039-3681. Bibcode: 2012SHPSA..43..182S. https://www.sciencedirect.com/science/article/abs/pii/S0039368111001373.
- Sandkühler, Hans Jörg, ed (2010). "Skepsis/Skeptizismus". Enzyklopädie Philosophie. Meiner. https://meiner.de/enzyklopadie-philosophie-14071.html.
- Baghramian, Maria; Carter, J. Adam (2022). "Relativism: 4.4 Epistemic relativism". Metaphysics Research Lab, Stanford University. https://plato.stanford.edu/entries/relativism/#EpiRel.
- John, Laursen. "Skepticism". New Dictionary of the History of Ideas. https://www.encyclopedia.com/philosophy-and-religion/philosophy/philosophy-terms-and-concepts/skepticism.
- Raynaud, Maurice (1 May 1981). "Skepticism in Medicine: Past and Present". The Linacre Quarterly 48 (2). ISSN 0024-3639. https://epublications.marquette.edu/lnq/vol48/iss2/8/.
- Cohen, Stewart (1996). Craig, Edward. ed. Routledge Encyclopedia of Philosophy. Routledge. https://philpapers.org/rec/BEAREO.
- Olsson, Erik J. (2005). "Not Giving the Skeptic a Hearing: "Pragmatism and Radical Doubt"". Philosophy and Phenomenological Research 70 (1): 98–126. doi:10.1111/j.1933-1592.2005.tb00507.x. ISSN 0031-8205. https://www.jstor.org/stable/40040781.
- Lagerlund, Henrik (29 April 2020) (in en). Skepticism in Philosophy: A Comprehensive, Historical Introduction. Routledge. p. 197. ISBN 978-1-351-36995-4. https://books.google.com/books?id=UX3gDwAAQBAJ&pg=PT197.
- Daly, Chris (2015). "Introduction and Historical Overview" (in en). The Palgrave Handbook of Philosophical Methods. Palgrave Macmillan UK. pp. 1–30. doi:10.1057/9781137344557_1. ISBN 978-1-137-34455-7. https://link.springer.com/chapter/10.1057/9781137344557_1.
- Matilal 2004, pp. 52–75.
- Diogenes Laërtius (tr. Hicks, 1925), ix.72. See also Bakalis (2005, p. 86)
- W. T. Jones, A History of Western Philosophy. New York: Harcourt, Brace, 1952, p. 60 n. 45.
- Richard H. Popkin, "Skepticism", in Paul Edwards, ed., The Encyclopedia of Philosophy, vol. 7. New York: Macmillan, 1967, p. 449.
- Allan Hazlett, A Critical Introduction to Skepticism. London: Bloomsbury, 2014, p. 4-5.
- Popkin, "Skepticism", p. 450.
- Daughtrity, D. (2017). Martin Luther: A Biography for the People. Abilene Christian University Press. p. 358. ISBN 978-0-89112-468-9. https://books.google.com/books?id=TEGHDwAAQBAJ&pg=PT358. Retrieved 2023-02-11.
- Richard H. Popkin, The History of Skepticism from Erasmus to Spinoza, rev. ed. Berkeley: University of California Press, 1979, chaps 1 and 2.
- See, e.g., Popkin, The History of Skepticism, p. 210.
- Quoted in Popkin, "Skepticism", p. 456.
- Popkin, "Skepticism", p. 456.
- Popkin, "Skepticism", p. 457.
- See, e.g., John Greco, ed., The Oxford Handbook of Skepticism. New York: Oxford University Press, 2008.
- Radford, Benjamin; Frazier, Kendrick (January 2017). "The Edge of Reason: A Rational Skeptic in an Irrational World". Skeptical Inquirer 41 (1): 60.
- Smith, Peter (2000). A Concise Encyclopedia of the Baháʼí Faith. Oxford, UK: Oneworld Publications. pp. 266–267. ISBN 1-85168-184-1.
- "Scientific Skepticism, CSICOP, and the Local Groups – CSI". July 1999. https://www.csicop.org/si/show/scientific_skepticism_csicop_and_the_local_groups.
- "AU 230 Due Professional Care in the Performance of Work" (in en-US). https://pcaobus.org/Standards/Auditing/Pages/AU230.aspx#ps-pcaob_1c410f9b-5033-4f18-b865-af1307863bee.
- A Greek-English Lexicon, Henry George Liddell and Robert Scott, revised and augmented throughout by Sir Henry Stuart Jones, with the assistance of Roderick McKenzie, Clarendon Press, Oxford, UK, 1940. Online, perseus.tufts.edu.
- Butchvarov, Panayot, Skepticism About the External World (Oxford University Press, 1998).
- Daniels, M.D., D.; Price, PhD, V. (2000), The Essential Enneagram, New York: HarperCollins
- Richard Hönigswald, Die Skepsis in Philosophie und Wissenschaft, 1914, new edition (ed. and introduction by Christian Benne and Thomas Schirren), Göttingen: Edition Ruprecht, 2008, ISBN:978-3-7675-3056-0
- Keeton, Morris T., "skepticism", pp. 277–278 in Dagobert D. Runes (ed.), Dictionary of Philosophy, Littlefield, Adams, and Company, Totowa, NJ, 1962.
- Le Morvan, P. (March 2011). "Healthy Skepticism and Practical Wisdom". Logos & Episteme (Institute for Economic and Social Research) 2 (1): 87–102. doi:10.5840/logos-episteme20112151. ISSN 2069-0533. http://logos-and-episteme.acadiasi.ro/wp-content/uploads/2015/02/HEALTHY-SKEPTICISM-AND-PRACTICAL-WISDOM.pdf.
- Webster's New International Dictionary of the English Language, Second Edition, Unabridged, W.A. Neilson, T.A. Knott, P.W. Carhart (eds.), G. & C. Merriam Company, Springfield, MA, 1950.
- Wilson, Richard (2009) (in en). Don't Get Fooled Again: A Sceptic's Handbook. Icon. ISBN 978-1848310520. https://books.google.com/books?id=RwFEOwAACAAJ.
- Popkin, Richard H. (2003) (in en). The History of Scepticism : From Savonarola to Bayle. Oxford University Press, US. ISBN 978-0198026716. https://books.google.com/books?id=7j8PdlgFRDAC.
- Bury, Robert Gregg (1933) (in en). Sextus Empiricus: Outlines of Pyrrhonism. Harvard University Press. ISBN 978-0674993013. https://books.google.com/books?id=8WPhjgEACAAJ.
- Empiricus, Sextus; Annas, Julia; Barnes, Jonathan (2000-07-20) (in en). Sextus Empiricus: Outlines of Scepticism. Cambridge University Press. ISBN 978-0521778091. https://books.google.com/books?id=mzO77w6KvDgC.
- Burnyeat, Myles (1983) (in en). The Skeptical Tradition. University of California Press. ISBN 978-0520037472. https://books.google.com/books?id=_5m2kdMwOswC.
- Rosa L; Rosa E; Sarner L; Barrett S (1998-04-01). "A close look at therapeutic touch". JAMA 279 (13): 1005–1010. doi:10.1001/jama.279.13.1005. ISSN 0098-7484. PMID 9533499.
- Novella, Steven (2018) (in en). The Skeptics' Guide to the Universe: How to Know What's Really Real in a World Increasingly Full of Fake. Hodder & Stoughton. ISBN 978-1473696419. https://books.google.com/books?id=4T5fDwAAQBAJ.
- Pearcey, Nancy (2005) (in en). Total Truth:Liberating Christianity from Its Cultural Captivity. Crossway Books. ISBN 978-1581347463. https://books.google.com/books?id=TZjfyuUJ9yQC.
- Thaxton, Charles (1994) (in en). The Soul of Science: Christian Faith and Natural Philosophy. Crossway Books. ISBN 978-0891077664. https://books.google.com/books?id=6lyoiNuypCUC.
- Skepticism at PhilPapers
- Skepticism at the Indiana Philosophy Ontology Project
- Klein, Peter. "Skepticism". in Zalta, Edward N.. Stanford Encyclopedia of Philosophy. https://plato.stanford.edu/entries/skepticism/.
- Vogt, Katja. "Ancient Greek Skepticism". in Zalta, Edward N.. Stanford Encyclopedia of Philosophy. https://plato.stanford.edu/entries/skepticism-ancient/.
- Thorsrud, Harald. "Ancient Greek Skepticism". Internet Encyclopedia of Philosophy. http://www.iep.utm.edu/skepanci/.
- Bolyard, Charles. "Medieval Skepticism". in Zalta, Edward N.. Stanford Encyclopedia of Philosophy. https://plato.stanford.edu/entries/skepticism-medieval//.
- Pritchard, Duncan. "Contemporary Skepticism". Internet Encyclopedia of Philosophy. http://www.iep.utm.edu/skepcont/.
- Skeptical Inquiry at Curlie
- "Most Scientific Papers are Probably Wrong" , New Scientist, 30 August 2005
- Classical Skepticism by Peter Suber
- "Outstanding skeptics of the 20th century" – Skeptical Inquirer magazine
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