How do you know your hands are real? This episode turns late-night thought experiments like the brain in a vat and Bertrand Russell’s five-minute-old universe into a serious tour of philosophical skepticism. We separate ordinary fact-checking skepticism from the radical kind that questions whether the external world exists at all, and explain the difference between local skepticism (moral truths, other minds) and radical skepticism (nothing can be known).

From there we trace how doubt has been used across history: Pyrrho and the ten modes of Sextus Empiricus as a path to ataraxia, Augustine’s two travelers at a fork in the road, Montaigne’s tracking dog, Descartes’ evil demon and cogito, Spinoza’s reading of scripture, and Hume’s problem of induction. We also look east to Jain many-sidedness and the blind men and the elephant, the Buddha’s thicket of views, and Zhuangzi’s butterfly dream, before G. E. Moore holds up his two hands and mitigated skepticism offers a livable middle ground.

• Why the ancient Pyrrhonists treated suspending judgment as a survival tool for mental peace
• Augustine’s argument that refusing to believe still leaves you vulnerable to the persuasive con man
• How Descartes used the most extreme doubt imaginable to find one unshakable certainty
• Hume’s problem of induction and why our belief in cause and effect is a habit of pattern recognition
• Mitigated skepticism and fallibilism: how to act with confidence while staying open to being wrong