e "active intelligence," from which, according to
him, intelligible species flow into our souls, and sensible species
into corporeal matter. And so Avicenna agrees with Plato in this, that
the intelligible species of our intellect are derived from certain
separate forms; but these Plato held to subsist of themselves, while
Avicenna placed them in the "active intelligence." They differ, too,
in this respect, that Avicenna held that the intelligible species do
not remain in our intellect after it has ceased actually to
understand, and that it needs to turn (to the active intellect) in
order to receive them anew. Consequently he does not hold that the
soul has innate knowledge, as Plato, who held that the participated
ideas remain immovably in the soul.

But in this opinion no sufficient reason can be assigned for the soul
being united to the body. For it cannot be said that the intellectual
soul is united to the body for the sake of the body: for neither is
form for the sake of matter, nor is the mover for the sake of the
moved, but rather the reverse. Especially does the body seem necessary
to the intellectual soul, for the latter's proper operation which is
to understand: since as to its being the soul does not depend on the
body. But if the soul by its very nature had an inborn aptitude for
receiving intelligible species through the influence of only certain
separate principles, and were not to receive them from the senses, it
would not need the body in order to understand: wherefore to no
purpose would it be united to the body.

But if it be said that our soul needs the senses in order to
understand, through being in some way awakened by them to the
consideration of those things, the intelligible species of which it
receives from the separate principles: even this seems an insufficient
explanation. For this awakening does not seem necessary to the soul,
except in as far as it is overcome by sluggishness, as the Platonists
expressed it, and by forgetfulness, through its union with the body:
and thus the senses would be of no use to the intellectual soul except
for the purpose of removing the obstacle which the soul encounters
through its union with the body. Consequently the reason of the union
of the soul with the body still remains to be sought.

And if it be said with Avicenna, that the senses are necessary to
the soul, because by them it is aroused to turn to the "active
intelligence" from which it receives the