Full Idea
Even where there is the highest degree of obviousness, we cannot assume that we are infallible - a sufficient conflict with other obvious propositions may lead us to abandon our belief, as in the case of a hallucination afterwards recognised as such.
Gist of Idea
The most obvious beliefs are not infallible, as other obvious beliefs may conflict
Source
Bertrand Russell (Regressive Method for Premises in Mathematics [1907], p.279)
Book Reference
Russell,Bertrand: 'Essays in Analysis', ed/tr. Lackey,Douglas [George Braziller 1973], p.279
A Reaction
This approach to fallibilism seems to arise from the paradox that undermined Frege's rather obvious looking axioms. After Peirce and Russell, fallibilism has become a secure norm of modern thought.