(4) There can be no real equality between God and the human soul, but God in His infinite goodness, elevating the soul to a higher plane and allowing it to participate in His own nature,[1085] makes possible an amicitia excellentiae s. eminentiae, which is sufficient to constitute a true relation of friendship. Without this elevation of the soul by grace there could be no friendship between God and man.[1086]
4. Adoptive Sonship.—The formal effects of sanctifying grace culminate in the elevation of man to the rank of an adopted child of God (filius Dei adoptivus), with a claim to the paternal inheritance, i.e. the beatific vision in Heaven. This truth is so clearly stated in Scripture and Tradition that its denial would be heretical. The Tridentine Council summarily describes justification as “the state of grace and of the adoption of the sons of God,”[1087] The teaching of Holy Scripture can be gathered from such texts as the following. Rom. VIII, 15 sqq.: “... You have received the spirit of adoption of sons, whereby we cry: Abba (Father). For the spirit himself giveth testimony to our spirit, that we are the sons of God. And if sons, heirs also; heirs indeed of God, and joint heirs with Christ.”[1088] 1 John III, 1 sq.: “Behold what manner of charity the Father hath bestowed upon us, that we should be called, and should be the sons of God.... Dearly beloved, we are now the sons of God.”[1089] Gal. IV, 5: “... that we might receive the adoption of sons.”[1090] That the just become the adopted [pg 357] sons of God follows likewise as a corollary from the doctrine of regeneration so frequently taught by Scripture. This regeneration is not a procession of the soul from the divine essence, but a kind of accidental and analogical procreation substantially identical with adoption (filiatio adoptiva, υἱοθεσία). Cfr. John I, 12 sq.: “... He gave them power to be made the sons of God, ... who are born ... of God.”[1091]
a) St. Thomas defines adoption as “the gratuitous acceptance of a child of other parents to be the same as one's own child and heir.”[1092] Adoption implies (1) that the adopted child be a stranger to the adopting father; (2) that it have no legal claim to adoption; (3) that it give its consent to being adopted; (4) that it be received by the adopting father with parental love and affection. All these elements are present, in a far higher and more perfect form, in the adoption of a soul by God.
(1) The rational creature, as such, is not a “son” but merely a “servant of God,”[1093] and, if he be in the state of mortal sin, His enemy.
(2) That adoption is a gratuitous favor on the part of the Almighty, follows from the fact that the adopted creature is His enemy and that grace is a free supernatural gift, to which no creature has a natural claim. Adoption furthermore implies the right of inheritance.[1094] [pg 358] The heritage of the children of God is a purely spiritual possession which can be enjoyed simultaneously by many, and consequently excels every natural heritage. Men, as a rule, do not distribute their property during life, while, after their death, it is usually divided up among several heirs.[1095]
(3) Whereas adoption among men owes its existence to the desire of offspring on the part of childless parents, the adoption of the soul by God springs from pure benevolence and unselfish love, and for this reason presupposes (in the case of adults) the free consent of the adopted. No one can become an adopted son of God against his will.[1096]
(4) Whereas human adoption supposes substantial equality between father and child, and therefore at best amounts to no more than a legal acceptance, adoption by God elevates the soul to a higher level by allowing it to participate in the Divine Nature, and consequently is a true (even though merely an accidental and analogical) regeneration in God.
b) From what we have said it follows—and this is a truth of considerable speculative importance—that there are essential points of difference as well as of resemblance between Jesus Christ, the true Son of God, and the justified sinner adopted by the Heavenly Father.
α) The difference between the “natural Son of God” and an “adopted son” is exactly like that between God and creature. The Logos-Son, engendered by eternal generation from the divine substance, is the true natural Son of the Father, the Second Person of the Divine Trinity, and Himself God.[1097] The just man, on the [pg 359] other hand, is a child of God merely by the possession of sanctifying grace,[1098] which can be lost by mortal sin and consequently is founded upon a free relation that may be terminated by man as freely as it was entered into between himself and God.
Intimately related to this distinction is another:—Christ is the Son of the Father alone, the just man is an adopted child of the whole Trinity.[1099] This fact does not, however, prevent us from “appropriating” adoptive sonship to each of the three Divine Persons according to His peculiar hypostatic character:—the Father as its author, the Son as its pattern, and the Holy Ghost as its conveyor.[1100] Now, if Christ, as the true Son of God, is the efficient cause (causa efficiens) of that adoptive sonship of which, as God, He is also the pattern-exemplar (causa exemplaris), it follows that He cannot be an adopted son of God. “Christus est incapax adoptionis,” as Suarez puts it.[1101] To say that He is both the natural and an adopted Son of God would be heretical.[1102] Consequently, sanctifying grace, in Him, did not exercise one of the functions it invariably exercises in the souls of men, i.e. it did not make Him an adopted son of God.