Full Idea
Knowledge is superior in value to opinion because it has certainty or complete absence of doubt.
Gist of Idea
Knowledge is superior to opinion because it is certain
Source
W. David Ross (The Right and the Good [1930], §VI)
Book Reference
Ross,W.David: 'The Right and the Good' [OUP 1930], p.147
A Reaction
This strikes me as a classic blunder, dating back to Descartes, which I think of as 'setting the bar too high'. It leads without fail to scepticism, because certainty is simply impossible for human beings. I am a committed fallibilist about knowledge.