9. To the objection that an intellect of infinite completeness reflects upon itself with infinite reflections, etc.: it must be said that in the divine intellect to understand and to understand that one understands are the same, even if understanding were iterated a thousand times and infinitely, because in God the one understanding, the thing understood, and the act of understanding are the same; and therefore that first act itself by which God the Father understands Himself is most actual and most complete, as is also the Word corresponding to it; and therefore it is not necessary on this account to introduce a plurality of words in the divine persons. But it is otherwise in the created intellect, whose act and operation differs from the one understanding and the thing understood, and therefore it can be multiplied, iterated, and enumerated more and more by the frequent turning of the intellect upon itself as understanding and upon its own act of understanding, and also upon things other than itself.
10. To the last objection, that either God can understand more persons, or He cannot: it must be said that not being able to understand more persons can be understood in two ways: either on account of a limitation of the intellect in the act of understanding, or on account of the rectitude of judgment and the impossibility of declining from the way of truth. In the first way it does not befit the divine intellect, since it is immense, but in the second way it does. Whence, that He cannot understand more persons means this: because such an understanding, although it might seem powerful in the act of understanding, nevertheless in reality declines from truth by understanding this and falls into error. Whence, just as the immensity of truth is entirely unmixed with falsity, so also the immensity of the light of understanding renders the divine intellect utterly free from all error; on account of which the divine intellect grasps neither something greater than itself, nor another God, nor a plurality of persons beyond the number three—not because it is limited, but because it is most perfectly infinite.
And from these things the solution to the whole question is clear.