Full Idea
Propositional content is inseparable from possible error. Therefore no judgement, however modest, is indubitable. So if basic experiential knowledge has to be indubitable, there is no such knowledge.
Gist of Idea
Propositions make error possible, so basic experiential knowledge is impossible
Source
Michael Williams (Problems of Knowledge [2001], Ch. 8)
Book Reference
Williams,Michael: 'Problems of Knowledge' [OUP 2001], p.100