Full Idea
No one who has a true idea is ignorant that a true idea involves the highest certitude; to have a true idea signifying just this, to know a thing perfectly or as well as possible.
Gist of Idea
True ideas intrinsically involve the highest degree of certainty
Source
Baruch de Spinoza (The Ethics [1675], II Pr 43)
Book Reference
Spinoza,Benedict de: 'Ethics', ed/tr. White,WH/Stirling,AH [Wordsworth 2001], p.82
A Reaction
This wildly optimistic view is found in rationalists of the period. Rationalism only becomes tolerable if fallibilism is added to it. See Bonjour.