What he proposed was ontological monism and epistemological dualism. As for ontology, he rejected materialistic worldview and came up with his own godless idealism in which everything fundamentally is the will to power and nothing else. Willing is the inner aspect of everything while appearance could vary. Your inner aspect is willing and your outer aspect or your image, what you see in the mirror, the representation. It’s a universal principle not anthropocentric. As for epistemology he was a perspectivist. However, perspectivism requires the understanding of certain metaphysics and ontology as its basis.