4. But, soul reached, why need we look higher; why not make this The First?
A main reason is that the Intellectual-Principle is at once something other and something more powerful than Soul and that the more powerful is in the nature of things the prior. For it is certainly not true, as people imagine, that the soul, brought to perfection, produces Intellect. How could that potentiality come to actuality unless there be, first, an effective principle to induce the actualization which, left to chance, might never occur?
The Firsts must be supposed to exist in actuality, looking to nothing else, self-complete. Anything incomplete must be sequent upon these, and take its completion from the principles engendering it which, like fathers, labour in the improvement of an offspring born imperfect: the produced is a Matter to the producing principle and is worked over by it into a shapely perfection.
And if, further, soul is passible while something impassible there must be or by the mere passage of time all wears away, here too we are led to something above soul.
Again there must be something prior to Soul because Soul is in the world and there must be something outside a world in which, all being corporeal and material, nothing has enduring reality: failing such a prior, neither man nor the Ideas would be eternal or have true identity.
These and many other considerations establish the necessary existence of an Intellectual-Principle prior to Soul.