This paper examines the implications of the Doctrine of Specific Nerve Energies for contemporary philosophy and psychology. Part I analyzed Johannes Peter Muller’s canonical formulation of the Doctrine, arguing that it follows from empirical results combined with methodological principles. Here, I argue that these methodological principles remain valid in psychology today, consequently, any naturalistic philosophy of perception must accept the Doctrine’s skeptical conclusion, that the qualities of our perceptual experience are not determined by, and thus do not reveal the nature (...) of, their causes in the world. Nevertheless, this does not mean that we must be global skeptics; rather, I argue that contemporary epistemology of perception should embrace Muller’s own response to the Doctrine: epistemic structural realism. As articulated by Muller’s student, Helmholtz, structural realism follows from the Doctrine once we recognize that active exploration constitutes part of the mechanism that determines perceptual experience, a view congenial to contemporary theories of embodied perception in cognitive science. Structural realists in philosophy of science should likewise heed the lessons of the Doctrine, as it played a critical part in the early history of their view, and may still serve a constructive role as exemplar today. (shrink)