On the Subject of the Soul

Our body, when it is put in action, is put in action either from without or from within. And that it is not put in action from without, is manifest from the circumstance that it is put in action neither by impulsion nor by traction, like soulless things. And again, if it is put in action from within, it is not put in action according to nature, like fire. For fire never loses its action as long as there is fire; whereas the body, when it has become dead, is a body void of action. Hence, if it is put in action neither from without, like soulless things, nor according to nature, after the fashion of fire, it is evident that it is put in action by the soul, which also furnishes life to it. If, then, the soul is shown to furnish the life to our body, the soul will also be known for itself by its operations.