Full Idea
General certainty is never to be found but in our ideas.
Gist of Idea
General certainty is only found in ideas
Source
John Locke (Essay Conc Human Understanding (2nd Ed) [1694], 4.06.16)
Book Reference
Locke,John: 'Essay Concerning Human Understanding', ed/tr. Nidditch,P.H. [OUP 1979], p.591
A Reaction
This is a fairly standard empirical view of such things. The obvious opposition to it might be Moore's 'hand' example (Idea 6349), if we ask, which is more certain, this hand I hold up, or this complex proof in mathematics?