X. Concerning the Boundary between the Physical World and Supersensible Worlds

If, however, the human soul were to develop in the physical world the capacity for transformation necessary for the elemental world, its personal identity would be lost. Such a soul would be living in contradiction with itself. In the physical world, the capacity for transformation must be a power at rest in the depths of the soul; a power which gives the soul its fundamental tone or keynote, but which does not come to development in that world.