Thus, Man is the species of species (naw' al-anwa'), Substance is the genus of genera (jins al-ajnas), and the growing body (al-jism al-nami) and Animal are intermediate sub-genera (jins mudaf); for when they are related to what is above them, they are called its species.

The Soul is a spiritual substance, alive by its very essence; when it couples with any physical body, it renders it alive like itself, just as fire is a corporeal substance, hot by its very essence, which when it comes into proximity with any physical body, renders it hot like itself.

As for the Soul—meaning the spirit—it is a celestial, luminous substance, alive by its very essence, knowing and active by nature, sensitive and perceptive potentially (drrakah bi-al-quwwah). It never rests nor ceases its movement so long as it exists; thus did its Lord fashion it on the day He created and brought it into being. It neither dies nor perishes; rather, it remains eternalized (mu'abbadah), either experiencing bliss or enduring pain.

However, particular animal souls may be afflicted with diseases that drive them away from equilibrium (al-i'tidal).