Full Idea
There is intuitive knowledge when the mind perceives the truth as the eye doth light (white is not black, the circle is not a triangle). This knowledge is the clearest and most certain...on this depends the certainty and evidence of all knowledge.
Gist of Idea
Intuition gives us direct and certain knowledge of what is obvious
Source
John Locke (Essay Conc Human Understanding (2nd Ed) [1694], 4.02.01)
Book Reference
Locke,John: 'Essay Concerning Human Understanding', ed/tr. Nidditch,P.H. [OUP 1979], p.531
A Reaction
Locke is different because he doesn't just talk of intuition, but of intuitive 'knowledge'. He has the standard problems of discriminating between good and bad intuitions, weak and strong, yours versus mine. Compare Russell's 'knowledge by acquaintance'.