 The arguments Lange deploys are drawn from research into the physiology of perception, by materialist researchers and by Helmholtz himself. For example, Lange claims that the physiology of our eyes shows that the visual sensation of a single three-dimensional object in front of me is in fact a composite generated from the two two-dimensional stimulations of each of my retinas (Lange 1873–75, 3:203). Supposedly we learn that even the simplest of sensations is not the result of a single natural process, but the combination of many different processes (3:203–204). Furthermore, we learn that “colours, sounds, smells, &amp;c., do not belong to things in themselves, … they are peculiar forms of excitation of our sensibility, which are called forth by corresponding but qualitatively very different phenomena in the world” (3:217). Indeed, according to these physiological accounts, only a very specific set of vibrations is picked out and the rest are ignored (3:217). We learn that there is a blind spot on the retina but that the brain fills in the spot when constructing our image of the world (3:220). The conclusion Lange wants us to draw from all of this is that the world we think we see is radically different from the way the world really is by materialism’s own lights.