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Verificationism: All perception must be translatable into perception sentences. If Apple is a meaningful concept, it is in red, round, sour, etc. translatable.
There are several spectral mixtures that cause the same color impression! Fig: I 122 different curves for "Lemon Yellow" (> color).
For this reason, the quality of the perception remains indefinable.
A. C. Danto
The Philosophical Disenfranchisement of Art (Columbia Classics in Philosophy) New York 2005