IV. Whether the Soul is Incorporeal.
That the soul is in our body, has been shown above. We ought now, therefore, to ascertain in what manner it is in the body. Now, if it is in juxtaposition with it, as one pebble with another, it follows that the soul will be a body, and also that the whole body will not be animated with soul, [451] inasmuch as with a certain part it will only be in juxtaposition. But if again, it is mingled or fused with the body, the soul will become multiplex, [452] and not simple, and will thus be despoiled of the rationale proper to a soul. For what is multiplex is also divisible and dissoluble; and what is dissoluble, on the other hand, is compound; [453] and what is compound is separable in a threefold manner. Moreover, body attached to body makes weight; [454] but the soul, subsisting in the body, does not make weight, but rather imparts life. The soul, therefore, cannot be a body, but is incorporeal.
Again, if the soul is a body, it is put in action either from without or from within. But it is not put in action from without; for it is moved neither by impulsion nor by traction, like soulless things. Nor is it put in action from within, like objects animated with soul; for it is absurd to talk of a soul of the soul: it cannot, therefore, be a body, but it is incorporeal.
And besides, if the soul is a body, it has sensible qualities, and is maintained by nurture. But it is not thus nurtured. For if it is nurtured, it is not nurtured corporeally, like the body, but incorporeally; for it is nurtured by reason. It has not, therefore, sensible qualities: for neither is righteousness, nor courage, nor any one of these things, something that is seen; yet these are the qualities of the soul. It cannot, therefore, be a body, but is incorporeal.
Still further, as all corporeal substance is divided into animate and inanimate, let those who hold that the soul is a body tell us whether we are to call it animate or inanimate.
Finally, if every body has colour, and quantity, and figure, and if there is not one of these qualities perceptible in the soul, it follows that the soul is not a body. [455]