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L. E. J. Brouwer (in his 1908 opening salvo against David Hilbert's mathematical formalism and the Law of the Excluded Middle) is clearly channeling Schopenhauer
Here's Schopenhauer, footnote 40 in §15 of Volume I of WWR "what is true and excellent in [Spinoza's] doctrine is in his case, as in that of geometry, quite independent of the proofs."
Here's a new translation of the Brouwer if you are as weird as I am arxiv.org/pdf/1511.01113.pdf
Apparently I did another thread on this topic