“While other philosophers of the time naively went about constructing theories of how the brain absorbed true knowledge through the senses (with an admixture of regrettable errata), Nietzsche drew an analogy from his first academic specialty: philology, or the study and interpretation of ancient texts. From the same text, two different scholars could draw opposite conclusions about the meaning of a word or phrase, because each entered with a larger contextual scheme in which the new text had to fit. In the arena of the mind, he suggested, different interpretations existed and gave different meanings to the same external data. An optical illusion, for instance, could be simultaneously read as a 3-dimensional image and a 2-dimensional illusion.

Had Nietzsche stopped with that analogy, it would have been just one more argument for epistemological relativism; and indeed, plenty of modern people read him with just that interpretive scheme in mind. But there was one key further ingredient: not all interpretations were created equal, and they vied with one another for dominance at every moment. And where they clash, some are stronger than others.”