Full Idea
An 'opinion' is taking something to be true which is subjectively and objectively insufficient. 'Believing' is when it is subjectively sufficient and objectively insufficient. 'Knowing' is subjective and objective sufficiency (for myself, and everyone).
Gist of Idea
Opinion is subjectively and objectively insufficient; belief is subjective but not objective; knowledge is both
Source
Immanuel Kant (Critique of Pure Reason [1781], B850/A822)
Book Reference
Kant,Immanuel: 'Critique of Pure Reason', ed/tr. Guyer,P /Wood,A W [CUO 1998], p.686
A Reaction
He defines objectivity as being 'sufficient' for 'everyone'. Compare Aristotle's Idea 95. This implies a rather social criterion for knowledge, but doesn't deal with 'sufficient for a majority, but not everyone'. How high to set the bar?
Related Idea
Idea 95 If everyone believes it, it is true [Aristotle]