 Right from his first acquaintance with Descartes’s philosophy, therefore, More believed that, like him, Descartes supposed that explanations of physical phenomena in terms of material principles could only take us so far, and beyond that point it was necessary to acknowledge the role of incorporeal active principles. In so far as Descartes did believe this, for him the boundary demarcating what could be explained in material terms and what could not, was a long way beyond where More would want to place it.