Radical skepticism or radical scepticism is the philosophical position that knowledge is most likely impossible. Radical skeptics hold that doubt exists as to the veracity of every belief and that certainty is therefore never justified. To determine the extent to which it is possible to respond to radical skeptical challenges is the task of epistemology or "the theory of knowledge".
In modern philosophy, two representatives of radical skepticism are Michel de Montaigne (most famously known for his skeptical remark, Que sçay-je?, 'What do I know?' in Middle French; modern French Que sais-je?) and David Hume (particularly as set out in A Treatise of Human Nature, Book 1: "Of the Understanding").
As radical skepticism can be used as an objection for most or all beliefs, many philosophers have attempted to refute it. For example, Bertrand Russell wrote “Skepticism, while logically impeccable, is psychologically impossible, and there is an element of frivolous insincerity in any philosophy which pretends to accept it.”
- Feyerabend, Paul (1999). For and against Method. Chicago: University of Chicago Press. p. 395. ISBN 0-226-46775-9.
- Dancy, Jonathan (1993). A Companion to Epistemology. Oxford: Blackwell. p. 89. ISBN 0-631-19258-1.
- Russell, Bertrand (1948). Human knowledge, its scope and limits. New York: Simon and Schuster. p. 9. OCLC 373835.
- The Epistemology Page
- Leavitt, Fred (2013) An Even Greater Scandal: I'm a Liar but You're a Bigger One. Strategic Book Publishing.