The spiritual immortal part in human beings that animates their body. Though a substance in itself, the soul is naturally ordained toward a body; separated, it an "incomplete" substance. The soul has no parts, it is therefore simple, but it is not without accidents. The faculties are its proper accidents. Every experience adds to its accidental form. It is individually created for each person by God and infused into the body at the time of human insemination. It is moreover created in respect to the body it will inform, so that the substance of bodily features and of mental characteristics insofar as they depend on organic functions is safefuarded. As a simple and spiritual substance, the soul cannot die. Yet it is not the total human nature, since a human person is composed of body animated by the soul. In philosophy, animals and plants are also said to have souls, which operate as sensitive and vegetative principles of life. Unlike the human spirit, these souls are perishable. The rational soul contains all the powers of the two other souls and is the origin of the sensitive and vegetative functions in the human being.