Full Idea
It is to me a sufficient reason not to believe the existence of anything, if I see no reason for believing it.
Gist of Idea
I do not believe in the existence of anything, if I see no reason to believe it
Source
George Berkeley (Three Dialogues of Hylas and Philonous [1713], II p.205)
Book Reference
Berkeley,George: 'The Principles of Human Knowledge etc.', ed/tr. Warnock,G.J. [Fontana 1962], p.205
A Reaction
This may just be a reasonable application of Ockham's Razor, but I fear that Berkeley painted himself into corner by demanding too many 'reasons' for everything.