Bertrand Russell once received a letter from logician Christine Ladd-Franklin declaring herself a solipsist and expressing surprise that there were no others. That unintentional punchline opens an exploration of solipsism, the position that only your own mind is certain to exist. Starting with Descartes' project of radical doubt and the three presuppositions that fuel solipsistic thought, the episode lays out the three flavors of the idea: metaphysical, epistemological, and methodological solipsism, and why the last is treated as a stress test for reality rather than a belief system.

From there the discussion moves through materialism versus idealism, Berkeley's claim that to be is to be perceived, the egocentric predicament, Leibniz's identity of indiscernibles, and the philosophical zombie. It then turns East to Advaita Vedanta, the Yoga  ...