Full Idea
The world which surrounds man exists only as idea - that is, only in relation to something else, the one who conceives the idea, which is himself. If any truth can be enunciated a priori, it is this.
Gist of Idea
The world only exists in relation to something else, as an idea of the one who conceives it
Source
Arthur Schopenhauer (The World as Will and Idea [1819], I 001)
Book Reference
Schopenhauer,Arthur: 'The World as Will and Idea', ed/tr. Berman,Jill and David [Everyman 1995], p.3
A Reaction
Yes, but the idea we have is of a real world. It is definitely not part of the idea that it is an idea (unlike my idea for a Christmas present).