Full Idea
Of any connection beyond the limits of my consciousness I cannot speak. ...I cannot proceed a hair's breadth beyond this consciousness, any more than I can spring out of myself.
Gist of Idea
There is nothing to say about anything which is outside my consciousness
Source
Johann Fichte (The Vocation of Man [1800], p.74), quoted by A.W. Moore - The Evolution of Modern Metaphysics 06.3
Book Reference
Moore,A.W.: 'The Evolution of Modern Metaphysics' [CUP 2013], p.154
A Reaction
I can't see that this is any different from the idealism of Berkeley, although they get there from different starting points. Idealist seem unable to even begin explaining consciousness.