All things with life have a principle of life that brings organic unity to a thing. If animals did not have souls, for example, their organ systems and tissues would not work in harmony. Even in plants, a soul must order all of its activities in a way that enables the plant to live. Take, for example, an animal. Even after an animal dies it may exhibit some of the functioning of a living thing for a while. Its heart may beat, parts of its nervous system may work, various cells in its bodies will still function. Why then is the animal dead? Because these various vital operations which may persist for a time after death no longer function in unison. There is no soul to bring organic unity to the thing and produce the conditions necessary for life. It just so happens that the human soul has the powers of intelligence and will, which are totally spiritual. Hence, only the souls of men subsist beyond physical death. The souls of plants and animals are so wholly bound up with their bodies that they do not persist beyond physical death. They corrupt upon the death of the physical body for plants and animals.