Truth is the relation of a judgment to something outside it as its sufficient reason.
 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 truth judgment
Date 1819
Language English
Reference
Note Translated by R. B. Haldane and J. Kemp
Weblink http://www.gutenberg.org/files/40868/40868-h/40868-h.html

Context

“A subject is equal to the sum of its predicates. (2.) A subject cannot at once have a given predicate affirmed and denied of it. (3.) Of two contradictorily opposed predicates one must belong to every subject. (4.) Truth is the relation of a judgment to something outside it as its sufficient reason. Reason, it may be remarked, has no material but only formal truth. Chapter VI. The third class of objects for the subject is constituted by the formal element in perception, the forms of outer and inner sense, space and time.” source