 As case 1 demonstrates, Fechner still holds an aether theory. He even includes the aether into his summary of his doctrine, according to which ponderable matter consists in spatially discrete parts, in between which there is an imponderable substance or aether (Atom: 79). Fechner admits, however, that there is much uncertainty about the relation of ponderable to imponderable matter. He knew that the aether theory was problematic, though this did not stop him from referring to Cauchy’s experiments. In the introduction to Part I of Atomlehre, he is explicit that atomism does not depend on the theory of aether (Atom: 14–15). The question whether light or heat are atomistically explicable is independent of the existence of the aether, he insists. 