Full Idea
No proposition can be said to be in the mind, which it never yet knew, which it was never yet conscious of.
Gist of Idea
A proposition can't be in the mind if we aren't conscious of it
Source
John Locke (Essay Conc Human Understanding (2nd Ed) [1694], 1.02.05)
Book Reference
Locke,John: 'Essay Concerning Human Understanding', ed/tr. Nidditch,P.H. [OUP 1979], p.50
A Reaction
This raises an interesting question. If we believe in the influence of the unconscious, we will have to talk of unconscious beliefs which affect our behaviour. We certainly all have beliefs of which we are not conscious. "Elvis had two feet".