Full Idea
I argue for the thesis that no one ever knows about anything, ...and that consequently no one is ever justified or at all reasonable in anything.
Gist of Idea
No one knows anything, and no one is ever justified or reasonable
Source
Peter Unger (Ignorance: a Case for Scepticism [1975], Intro)
Book Reference
Unger,Peter: 'Ignorance: a Case for Scepticism' [OUP 1975], p.1
A Reaction
The premiss of his book seems to be that knowledge is assumed to require certainty, and is therefore impossible. Unger has helped push us to a more relaxed and fallibilist attitude to knowledge. 'No one is reasonable' is daft!