I say, as Isidorus says, that there are two lives: the life called nutritive, and the life called sensory.255 Taking the spirit as the life force, it is said that it is the first instrument of the soul. And thus Galen says that the body consists of that which carries, and that which is carried. The force is the carrier or
p.127the active spirit along with the force which it carries; therefore I say, the body is heavier dead than living, because of the loss of the spirit that carries and lightens it. In the same way Galen says there is erective force in the body of a man standing, for if there were not, he would fall. This is clear in the case of weak people, for through the weakness of their erective force, they cannot remain standing. He says in like wise, of the bird which when flying through the air lingers hovering by virtue of that spirit, for Avicenna says, the spirit is the carrier of the force. Having regard to these facts, we say the spirit maintains and is root, and the heart is branch.