 Anxious to defend the concept of immaterial souls from all atheist threats, More insisted that the soul was necessary for life. He was therefore opposed not only to Descartes, but also to traditional scholastic views. The motions of plants and animals (plants being capable of internal motions associated with nutrition, reproduction, and growth), according to scholastics, proved the existence only of vegetative and animal souls respectively. Both of these kinds of souls were regarded as material, however, being composed of subtle fluids or tenuous but nonetheless material spirits in the body. Descartes simply absorbed the functions of these material souls into his mechanistic theory of creature-as-automaton. By contrast, More, pursuing his overriding concern to deny atheists any footholds, ran counter to both Aristotelians and Cartesians and insisted on the immateriality of animal souls (and presumably vegetative souls, though he does not seem to discuss them). In More’s version of dualism only immaterial entities are self-active and capable of initiating movement in other entities, and so the fact that plants and animals can move themselves is taken to prove that they must have immaterial souls (Henry 1986, 1989; Reid 2012). It should be noted, therefore, that underlying More’s argumentation is a commitment to the belief that matter is essentially passive (capable only of inertial motions), and that only immaterial entities are active. This commitment, however, is not based on any original philosophical arguments developed by More himself. It is simply based on what More sees as a fundamental premise of Cartesianism, namely, that matter or body is completely inert and passive. This is why More seized upon Cartesianism so keenly. If matter is inert then the activity we see all around us must have another source, which must be immaterial. Underlying this, of course, was a desire to deny the claims of contemporary materialist (and therefore atheist) philosophers (Henry 1986, Leech 2013). 