We have dreams; may not our whole life be a dream? or more exactly: is there a sure criterion of the distinction between dreams and reality? between phantasms and real objects?
 Arthur Schopenhauer, The World as Will and Representation (1819). copy citation

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Author Arthur Schopenhauer
Source The World as Will and Representation
Topic reality distinction
Date 1819
Language English
Reference
Note Translated by R. B. Haldane and J. Kemp
Weblink http://www.gutenberg.org/files/38427/38427-h/38427-h.html

Context

“There [pg 020] is, however, one other possible origin of this question, quite different from the purely speculative one which we have considered, a specially empirical origin, though the question is always raised from a speculative point of view, and in this form it has a much more comprehensible meaning than it had in the first. We have dreams; may not our whole life be a dream? or more exactly: is there a sure criterion of the distinction between dreams and reality? between phantasms and real objects? The assertion that what is dreamt is less vivid and distinct than what we actually perceive is not to the point, because no one has ever been able to make a fair comparison of the two; for we can only compare the recollection of a dream with the present reality.” source