But, it may still be urged, if God wished to bring it about that we should perceive them, he would be obliged to endow us with a greater faculty of perception, but not a greater faculty of volition than we have already.

This is the same as to say that, if God wished to bring it about that we should understand an infinite number of other entities, it would be necessary for him to give us a greater understanding, but not a more universal idea of entity than that which we have already, in order to grasp such infinite entities.
We have shown that will is a universal entity or idea, whereby we explain all particular volitions--in other words, that which is common to all such volitions.
As, then, our opponents maintain that this idea, common or universal to all volitions, is a faculty, it is little to be wondered at that they assert, that such a faculty extends itself into the infinite, beyond the limits of the understanding: for what is universal is predicated alike of one, of many, and of an infinite number of individuals.
To the second objection I reply by denying, that we have a free power of suspending our judgment: for, when we say that anyone suspends his judgment, we merely mean that he sees, that he does not perceive the matter in question adequately.
Suspension of judgment is, therefore, strictly speaking, a perception, and not free will.

In order to illustrate the point, let us suppose a boy imagining a horse, and perceive nothing else.

Inasmuch as this imagination involves the existence of the horse (II.xvii.

Coroll.), and the boy does not perceive anything which would exclude the existence of the horse, he will necessarily regard the horse as present: he will not be able to doubt of its existence, although he be not certain thereof.