Objection 1. It would seem that the soul of Christ cannot know the infinite in the Word. For that the infinite should be known is repugnant to the definition of the infinite which (Phys. iii, 63) is said to be that "from which, however much we may take, there always remains something to be taken." But it is impossible for the definition to be separated from the thing defined, since this would mean that contradictories exist together. Therefore it is impossible that the soul of Christ knows the infinite.
Objection 2. Further, the knowledge of the infinite is infinite. But the knowledge of the soul of Christ cannot be infinite, because its capacity is finite, since it is created. Therefore the soul of Christ cannot know the infinite.
Objection 3. Further, there can be nothing greater than the infinite. But more is contained in the Divine knowledge, absolutely speaking, than in the knowledge of Christ's soul, as stated above (Article 2). Therefore the soul of Christ does not know the infinite.
On the contrary, The soul of Christ knows all its power and all it can do. Now it can cleanse infinite sins, according to 1 John 2:2: "He is the propitiation for our sins, and not for ours only, but also for those of the whole world." Therefore the soul of Christ knows the infinite.
I answer that, Knowledge regards only being, since being and truth are convertible. Now a thing is said to be a being in two ways: First, simply, i.e. whatever is a being in act; secondly, relatively, i.e. whatever is a being in potentiality. And because, as is said Metaph. ix, 20, everything is known as it is in act, and not as it is in potentiality, knowledge primarily and essentially regards being in act, and secondarily regards being in potentiality, which is not knowable of itself, but inasmuch as that in whose power it exists is known. Hence, with regard to the first mode of knowledge, the soul of Christ does not know the infinite. Because there is not an infinite number in act, even though we were to reckon all that are in act at any time whatsoever, since the state of generation and corruption will not last for ever: consequently there is a certain number not only of things lacking generation and corruption, but also of things capable of generation and corruption. But with regard to the other mode of knowing, the soul of Christ knows infinite things in the Word, for it knows, as stated above (Article 2), all that is in the power of the creature. Hence, since in the power of the creature there is an infinite number of things, it knows the infinite, as it were, by a certain knowledge of simple intelligence, and not by a knowledge of vision.
Reply to Objection 1. As we said in I, 8, 1, the infinite is taken in two ways. First, on the part of a form, and thus we have the negatively infinite, i.e. a form or act not limited by being received into matter or a subject; and this infinite of itself is most knowable on account of the perfection of the act, although it is not comprehensible by the finite power of the creature; for thus God is said to be infinite. And this infinite the soul of Christ knows, yet does not comprehend. Secondly, there is the infinite as regards matter, which is taken privatively, i.e. inasmuch as it has not the form it ought naturally to have, and in this way we have infinite in quantity. Now such an infinite of itself, is unknown: inasmuch as it is, as it were, matter with privation of form as is said Phys. iii, 65. But all knowledge is by form or act. Therefore if this infinite is to be known according to its mode of being, it cannot be known. For its mode is that part be taken after part, as is said Phys. iii, 62,63. And in this way it is true that, if we take something from it, i.e. taking part after part, there always remains something to be taken. But as material things can be received by the intellect immaterially, and many things unitedly, so can infinite things be received by the intellect, not after the manner of infinite, but finitely; and thus what are in themselves infinite are, in the intellect of the knower, finite. And in this way the soul of Christ knows an infinite number of things, inasmuch as it knows them not by discoursing from one to another, but in a certain unity, i.e. in any creature in whose potentiality infinite things exist, and principally in the Word Himself.
Reply to Objection 2. There is nothing to hinder a thing from being infinite in one way and finite in another, as when in quantities we imagine a surface infinite in length and finite in breadth. Hence, if there were an infinite number of men, they would have a relative infinity, i.e. in multitude; but, as regards the essence, they would be finite, since the essence of all would be limited to one specific nature. But what is simply infinite in its essence is God, as was said in I, 7, 2. Now the proper object of the intellect is "what a thing is," as is said De Anima iii, 26, to which pertains the notion of the species. And thus the soul of Christ, since it has a finite capacity, attains to, but does not comprehend, what is simply infinite in essence, as stated above (1). But the infinite in potentiality which is in creatures can be comprehended by the soul of Christ, since it is compared to that soul according to its essence, in which respect it is not infinite. For even our intellect understands a universal--for example, the nature of a genus or species, which in a manner has infinity, inasmuch as it can be predicated of an infinite number.
Reply to Objection 3. That which is infinite in every way can be but one. Hence the Philosopher says (De Coel. i, 2,3,) that, since bodies have dimensions in every part, there cannot be several infinite bodies. Yet if anything were infinite in one way only, nothing would hinder the existence of several such infinite things; as if we were to suppose several lines of infinite length drawn on a surface of finite breadth. Hence, because infinitude is not a substance, but is accidental to things that are said to be infinite, as the Philosopher says (Phys. iii, 37,38); as the infinite is multiplied by different subjects, so, too, a property of the infinite must be multiplied, in such a way that it belongs to each of them according to that particular subject. Now it is a property of the infinite that nothing is greater than it. Hence, if we take one infinite line, there is nothing greater in it than the infinite; so, too, if we take any one of other infinite lines, it is plain that each has infinite parts. Therefore of necessity in this particular line there is nothing greater than all these infinite parts; yet in another or a third line there will be more infinite parts besides these. We observe this in numbers also, for the species of even numbers are infinite, and likewise the species of odd numbers are infinite; yet there are more even and odd numbers than even. And thus it must be said that nothing is greater than the simply and in every way infinite; but than the infinite which is limited in some respect, nothing is greater in that order; yet we may suppose something greater outside that order. In this way, therefore, there are infinite things in the potentiality of the creature, and yet there are more in the power of God than in the potentiality of the creature. So, too, the soul of Christ knows infinite things by the knowledge of simple intelligence; yet God knows more by this manner of knowledge or understanding.
Source: Summa Theologica (New Advent)