Full Idea
Even if this whole life were said to be only a dream, and the visible world only a phantasm, I should call this dream or phantasm real enough if we were never deceived by it when we make good use of reason.
Gist of Idea
If experience is just a dream, it is still real enough if critical reason is never deceived
Source
Gottfried Leibniz (De modo distinguendi phaenomena [1685], A6.4.1502), quoted by Daniel Garber - Leibniz:Body,Substance,Monad 7
Book Reference
Garber,Daniel: 'Leibniz: Body, Substance, Monad' [OUP 2009], p.282
A Reaction
I find this response more satisfactory than his response in Idea 12740. As a supporter of the coherence account of justification, I take the closest we get to knowledge to be when our full critical faculties and experience are brought to bear, and shared.
Related Idea
Idea 12740 The strongest criterion that phenomena show reality is success in prediction [Leibniz]