Matter is the idea of the intelligence; the intelligence is that in whose idea alone matter exists.
 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 intelligence ideas
Date 1819
Language English
Reference
Note Translated by R. B. Haldane and J. Kemp
Weblink http://www.gutenberg.org/files/40097/40097-h/40097-h.html

Context

“I have shown this weak side of materialism in § 7 of the first volume. For me, on the contrary, matter and intelligence are inseparable correlates, which exist only for each other, and therefore merely relatively. Matter is the idea of the intelligence; the intelligence is that in whose idea alone matter exists. The two together constitute the world as idea, which is just Kant's phenomenon, and consequently something secondary. What is primary is that which manifests itself, the thing in itself, which we shall afterwards discover is the will.” source