The reason for selecting the human rather than the angelic nature for the hypostatic union is obvious from all that has preceded. Human nature is a microcosm, in which all grades of existence are summed up and represented. In taking human nature the Word assumes all created nature, from the lowest to the highest. For, although the angelic nature is superior to the human, it is only superior to it in certain respects, and not as a rational essence. Moreover, this superiority is part only temporary, enduring while the human nature is in the process of explication; and as to the rest, the inferiority of the human nature is counterbalanced by the supernatural elevation given to it in the hypostatic union, which raises the natural, human operation of the soul of our Lord Jesus Christ far above that of the angelic nature. Although, therefore, in the series of grades in the natural order of existence, the angelic nature is above the human, it is subordinated to it in the supernatural order, or the order of the incarnation, and in relation to the final cause. For it is through the human nature united to the divine nature in the person of the Word that the angelic nature completes its return to God and union with him.
The elevation of created nature to the hypostatic union with God in the person of the Word introduces an entirely new principle of life into the intelligent universe. Hitherto, we have considered in the creative act a regular gradation in the nature of created existences, from the lowest to the highest. Each grade is determined to a certain participation in being superior in intensity to that of the one below it and to a mode of activity corresponding to its essence. There can be no grade of existence in its essence superior to the rational or intelligent nature, which is created in the similitude of that which is highest in the divine essence. No doubt, the specific and minor grades included under the universal generic grade of rationality might be indefinitely multiplied. As the angels differ from man, and the various orders of the angelic hierarchy differ from each other, so God might continue to create ad infinitum new individuals or new species, each differing from all others, and all arranged in an ascending series, in which each grade should be superior in certain particulars to all below it. It is evidently possible that a created intelligence should be made to progress from the lowest stage of development continuously and for ever. Let us fix our thought upon the most distant and advanced limit in this progression which we are able to conceive. It is evident that God might have created an intelligent spirit in the beginning at that point, as the starting-point of his progression, and might have created at the same time other intelligent spirits at various distances from this point in a descending series. Suppose now that this is the case, and that the lowest in the scale progresses until he reaches the starting-point of the most advanced. The one who began at this advanced point will have progressed meanwhile to another point equally distant, and will preserve his relative superiority. But even at this point, God might have created him at first, with another series of intervening grades at all the intermediate points which he has passed over in his progressive movement. We may carry on this process as long as we please, without ever coming to a limit at which we are obliged to stop. For the creation being of necessity limited, and the creative power of God unlimited, it is impossible to equalize the two terms, or to conceive of a creation which is equal to God as creator. Nevertheless, [{148}] all possible grades of rationality are like and equal to each other as respects the essential propriety of rationality, and never rise to a grade which is essentially higher than that of rational nature. The only difference possible is a difference in the mode in which the active force of the intellect is exercised, and in the number of objects to which it is applicable, or some other specific quality of the same kind. Whatever may be the increase which rational nature can be supposed to receive, it is only the evolution of the essential principle which constitutes it rational, and is therefore common to all species and individuals of the rational order. Although, therefore, God cannot create a spirit so perfect that it cannot be conceived to be more perfect in certain particulars, yet it is nevertheless true that God cannot create anything which is generically more perfect than spirit or intelligent substance. From this it follows as a necessary consequence, that God cannot create a nature which by its essential principles demands its last complement of being in a divine person, or naturally exists in a hypostatic union with the divine nature. For rational nature, which is the highest created genus, and the nearest possible to the nature of God,—"Ipsius enim et genus sumus," [Footnote 32]—developed to all eternity, would never rise above itself, or elicit an act which would cause it to terminate upon a divine person, and bring it into a hypostatic union with God.
[Footnote 32: "For we are also his offspring." Acts xvii. 28.]
Produce a line, parallel to an infinite straight line, to infinity, and it will never meet it or come any nearer to it. The very essence of created spirit requires that it should be determined to a mode of apprehending God an image reflected in the creation. The activity of the created intelligence must proceed for ever in this line, and has no tendency to coincide with the act of the divine intelligence in which God contemplates immediately his own essence. Increase as much as you will the perfection of the created image, it remains always infinitely distant from the uncreated, personal image of himself which the Father contemplates in the Word, and loves in the Holy Spirit, within the circle of the blessed Trinity. It has been proved in a previous number that infinite intelligence is identical with the infinite intelligible in God. If a being could be created which by its essence should be intelligent by the immediate vision of the divine essence, it would be intelligent in se, and therefore possess within its own essence its immediate, intelligible object, which, by the terms of the supposition, is the divine essence. It would possess in itself sanctity, immutability, and beatitude. It would be, in other words, beatified precisely because existing, that is, incapable of existing in any defective state, and therefore incapable of error, sin, or suffering. And as, by the terms, it is what it is, by its essence, its essence and existence are identical; it is essentially most pure act, essentially existing, therefore self-existent, necessary being, or identical with God. It is therefore impossible for God to create a rational nature which is constituted rational by the immediate intuition of the divine essence. For by the very terms it would be a creature and God at the same time. It would be one of the persons in the unity of the divine nature, and yet have a nature totally distinct. In the natural order, then, it is impossible that a created nature should either at its beginning, or in the progress of its evolution, demand as its due and necessary complement of being a divine personality. Personality is the last complement of rational nature. Divine nature demands divine personality. Finite nature demands finite personality. It is evident, therefore, that there cannot be a finite nature, however exalted, which cannot come to its complete evolution within its own essence, or which can explicate out of the contents of its being an act which necessarily terminates upon a divine person, so as to bring it into a hypostatic union with the divine nature.
Let us go back a little in the scale of being, in order to develop this principal more fully. Lifeless matter is capable of indefinite increase in its own order, but this increase has no tendency to elevate it to the grade of vegetative life. A new and different principle of organization must be introduced in order to construct from its simple elements a vegetative form, as, for instance, a flower. So, also, the explication of vegetative life has no tendency to generate a sentient principle. The plant may go on producing foliage, flowering, germinating, and reproducing its species for ever, but its vital activity can never produce a sentient soul, or proceed to that degree of perfection that it requires a sentient soul as its last complement or the form of its organic life. Suppose a plant or flower to receive a sentient soul; this soul must be immediately created by God, and it would be the principle or form of a new life, which, in relation to the natural, vegetative life of the flower, would be super-natural, elevating it to an order of life above that which constitutes it a flower.
A sentient creature, as a dog or a bird, has no tendency to explicate from the constitutive principle of its animal soul intelligence, or to attain a state of existence in which an intelligent personality is due to it as its last complement. If the animal soul could have an intelligent personality, it must be by hypostatic union with an intelligent nature distinct from itself, which would then become the suppositum, or principal of imputability to the animal nature. The animal would then be elevated to a state which would be super-natural, relatively to the animal nature, or entirely above the plane of it's natural development.
In like manner, the rational nature has no tendency or power to rise above itself, or to do more than explicate that principle which constitutes it rational. If it is elevated to a higher order, it must be by a direct act of omnipotence, an immediate intervention of the creator, producing in it an act which could never be produced by the explication of its rationality, even though it should progress to all eternity. This act is supernatural in the absolute sense. That is, it lies in an order above created nature as a totality, and above all nature which might be created; supra omnem naturam creatam atque creabilem.
It is beyond the power even of divine omnipotence to create a rational nature which, by its intrinsic, constitutive principle of intelligence, is affiliated to the Father through the Holy Spirit. Such a nature would be equal to the Word, and another Word, and therefore equal to the Father, or, in other words, would be a divine nature although created; which is absurd. The Father can have but one Son, eternally begotten, not made; and the only possible way in which a created nature can be elevated to a strictly filial relation to the Father, is by a hypostatic union with the divine nature of the Son in one person, so that there is a communication of properties between the two natures, and but one principle of imputability to which all the divine and human attributes and acts can be referred. This union can be effected only by a direct intervention of God, or by the Word assuming to himself a created nature. For rational nature finds its last complement of personality, its subsistentia, or principle of imputability, within its own limits, which it never tends to transcend, even by infinite progression. The human nature individuated in the person of Jesus Christ, by its own intrinsic principles was capable of being completed in a finite personality, like every other individual human nature. The fact that the place of the human personality is supplied by a divine person, and the human nature thus completed only in the divine, is due to the direct, divine act of the Word, and is therefore supernatural. In this supernatural relation it becomes the recipient, so to speak, of the divine vital current, and participates in the [{150}] act in which the divine life is consummated, which is the procession of the Son and Holy Spirit from the Father. This act consists radically and essentially in the immediate contemplation of the divine essence. Created intelligence, therefore, elevated to the hypostatic union, contemplates the essence of God directly, without any intervening medium, by the immediate intuition or beatific vision of God.
Thus, in the incarnation, the creation returns back to God and is united to him in the most perfect manner, by participating in the good of being in a way sublime above all human conception, exhausting even the infinite idea of God. Created intelligence is beatified, glorified, and deified. In Jesus Christ, man, in whose essence is included the equivalent of all creation, and God meet in the unity of one person. The nature of God becomes the nature of man in the second person, who is truly man; and the nature of man becomes the nature of God in the same person, who is truly God. Creation, therefore, attains its final end and returns to God as final cause in the incarnation; which is the most perfect work of God, the crown of the acts of his omnipotence, the summit of the creative act, the completion of all grades of existence, and the full realization of the divine archetype.