Objection 1. It would seem that the soul of Christ could not understand by this knowledge except by turning to phantasms, because, as is stated De Anima iii, 18,31,39, phantasms are compared to man's intellective soul as colors to sight. But Christ's power of seeing could not become actual save by turning to colors. Therefore His intellective soul could understand nothing except by turning to phantasms.
Objection 2. Further, Christ's soul is of the same nature as ours. otherwise He would not be of the same species as we, contrary to what the Apostle says (Philippians 2:7) "... being made in the likeness of men." But our soul cannot understand except by turning to phantasms. Hence, neither can Christ's soul otherwise understand.
Objection 3. Further, senses are given to man to help his intellect. Hence, if the soul of Christ could understand without turning to phantasms, which arise in the senses, it would follow that in the soul of Christ the senses were useless, which is not fitting. Therefore it seems that the soul of Christ can only understand by turning to phantasms.
On the contrary, The soul of Christ knew certain things which could not be known by the senses, viz. separate substances. Therefore it could understand without turning to phantasms.
I answer that, In the state before His Passion Christ was at the same time a wayfarer and a comprehensor, as will be more clearly shown (15, 10). Especially had He the conditions of a wayfarer on the part of the body, which was passible; but the conditions of a comprehensor He had chiefly on the part of the soul. Now this is the condition of the soul of a comprehensor, viz. that it is nowise subject to its body, or dependent upon it, but wholly dominates it. Hence after the resurrection glory will flow from the soul to the body. But the soul of man on earth needs to turn to phantasms, because it is fettered by the body and in a measure subject to and dependent upon it. And hence the blessed both before and after the resurrection can understand without turning to phantasms. And this must be said of the soul of Christ, which had fully the capabilities of a comprehensor.
Reply to Objection 1. This likeness which the Philosopher asserts is not with regard to everything. For it is manifest that the end of the power of seeing is to know colors; but the end of the intellective power is not to know phantasms, but to know intelligible species, which it apprehends from and in phantasms, according to the state of the present life. Therefore there is a likeness in respect of what both powers regard, but not in respect of that in which the condition of both powers is terminated. Now nothing prevents a thing in different states from reaching its end by different ways: albeit there is never but one proper end of a thing. Hence, although the sight knows nothing without color; nevertheless in a certain state the intellect can know without phantasms, but not without intelligible species.
Reply to Objection 2. Although the soul of Christ was of the same nature as our souls, yet it had a state which our souls have not yet in fact, but only in hope, i.e. the state of comprehension.
Reply to Objection 3. Although the soul of Christ could understand without turning to phantasms, yet it could also understand by turning to phantasms. Hence the senses were not useless in it; especially as the senses are not afforded to man solely for intellectual knowledge, but for the need of animal life.
Source: Summa Theologica (New Advent)