What is Debate the Skeptic?
Debate the Skeptic is a free website where you can debate a virtual Pyrrhonian skeptic inspired by the ancient philosopher Sextus Empiricus. Bring any belief (about whether free will exists, say, or whether pineapple belongs on pizza), and the Skeptic gently asks what supports it. As you uncover your reasons, it creates an argument map of your belief, its supporting reasons, and their support relations.
Every line of justification eventually rests on a fundamental assumption, goes in a circle, or goes on forever (an infinite regress); this is Agrippa’s trilemma. When all lines of justification are seen to meet this fate, the Skeptic invites you to suspend judgment. You are rewarded with a certificate (tranquility to follow).
The Skeptic holds no views of their own. They merely report why others might disagree with a visitor’s belief without themselves arguing for the opposite belief. Every belief and reason comes from the visitor. The Skeptic may suggest implicit premises, but they never supply their own reasons for the visitor's belief.
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Why?
The aim is to offer a light-hearted introduction to philosophy and show how philosophical skills can be useful in everyday life. Debating the Skeptic can help us
- analyse the reasons supporting our beliefs,
- uncover our own implicit assumptions,
- see where justification runs out,
- and exercise intellectual humility, which brings us tranquility.
It also introduces Pyrrhonian skepticism, which aims not to win arguments or prove knowledge is impossible but rather to reach the suspension of judgment. The basic idea is that our beliefs ultimately rest on too shakey foundations to get worked up over. Once we realize this, tranquility (ataraxia) follows “as a shadow follows a body” (Sextus Empiricus 2000, I.29).
The Skeptic uses an argument map, which is a graphical depiction of a conclusion with its supporting reasons, to depict the visitor arguments. This helps both the Skeptic and the visitor better discern the structure of the visitor's argument. Research shows that practice in argument mapping can improve critical thinking and argument analysis (Twardy 2004; Harrell 2011; van Gelder 2015).
How does it work?
Under the hood, hard-coded rules constrain the permissible moves and manage the argument map, while AI (Anthropic’s Claude) interprets visitors’ contributions, selects among permitted moves, and generates the Skeptic’s natural-language replies. The end result is a regimented discussion driven by flexible and forgiving natural-language dialogue. This isn't just a chat bot. It's analogous to an AI playing chess with you where you describe to the AI your moves in ordinary language, it moves your piece for you, and then it decides on its own move.
Who made it?
Angela Mendelovici, Professor of Philosophy at Western University, Canada, designed and maintains the site. She first built The Skeptic in 2007 and revived and rebuilt it in 2026. The site is in beta and improving all the time, thanks partly to visitors’ feedback.
Your privacy
Debates are saved and may be read by the site’s maintainer for quality assurance and to improve the site. To remain anonymous, use a fake name and don’t share anything private.
The site does not use cookies. Usage limits use a one-way scrambled code derived from your internet address, not the address itself. See the FAQ.
Support
Each debate costs a few cents to run. Usage limits keep costs in check while the project seeks long-term support. To help support the project, contact Angela Mendelovici.
References
- Harrell, Maralee. 2011. Argument Diagramming and Critical Thinking in Introductory Philosophy. Higher Education Research & Development 30 (3): 371–385.
- Sextus Empiricus. 2000. Outlines of Scepticism. Translated by Julia Annas and Jonathan Barnes. 2nd ed. Cambridge: Cambridge University Press.
- Twardy, Charles R. 2004. Argument Maps Improve Critical Thinking. Teaching Philosophy 27 (2): 95–116.
- van Gelder, Tim. 2015. Using Argument Mapping to Improve Critical Thinking Skills. In The Palgrave Handbook of Critical Thinking in Higher Education, edited by Martin Davies and Ronald Barnett, 183–192. New York: Palgrave Macmillan.