 We will leave aside, for reasons of space, further complications in Fechner’s theory. To avoid serious confusion, though, it is necessary to consider, if only briefly, the origins of the  theory.[15]  Fechner himself stated that his theory had its roots in Schelling’s Naturphilosophie (Atom: xiv). There is a certain plausibility to Fechner’s genealogy. In the early 1800s Schelling had developed his own dual aspect theory of the mind and body, according to which the mental and physical, the ideal and the real, are two equal and independent appearances of the absolute. We need not cast doubt on Fechner’s genealogy. The initial impetus for his dual aspect theory might indeed have been Schelling; perhaps, if he had not read Schelling, he would never have suggested a dual aspect theory. Still, it is important to see that Fechner developed his theory along lines completely different from Schelling’s. It was a fundamental principle of Schelling’s theory that the mental and physical are one and the same because they are different manifestations or appearances of living force; the mental is the highest organization and development of that force, the physical is its lowest organization and development. His theory therefore rested upon the dynamic theory of matter central to his Naturphilosophie. But Fechner, as we have seen, rejected this theory, which was in conflict with his atomism. Furthermore, Schelling, like Spinoza, forbade the possibility of interaction between the mental and physical, the very possibility that Fechner wanted to investigate (Schelling 1859: I/4, 344). 