 Having pointed to phenomena in nature which cannot be explained in terms of the mechanical philosophy, More can introduce the concept of an active Spirit of Nature to fill in the lacunae. He therefore has provided, according to his own lights, a rational, philosophical, basis for the necessary existence of the Spirit of Nature, and by extension of spirit, or incorporeal substance more generally. This is crucial, of course, for More’s dualistic theology. It seems clear to us, as it must have for many contemporary readers, that the Spirit of Nature did not emerge from More’s understanding of the natural world, but from the demands of his rational dualist ontology. Preoccupied as he was with the need to establish a categorical dualism between inert matter and active incorporeal spirit, he was quick to see those parts of Descartes’s natural philosophy which were least plausible, or completely unconvincing, as providing what he took to be evidence for the necessary existence of the Spirit of Nature.