that what is proper to one nature can be ascribed to the other ("communicatio idiomatum," c. 5). The unity is not a mere inhabitation of the Creator in the created nature, but a real mingling of the one nature with the other, though they remain distinct (Serm. xxiii. § 1), and the result is "ut idem esset dives in paupertate, omnipotens in abjectione, impassibilis in supplicio, immortalis in morte" (Ep. xxxv. 2). Just as the visible light is contaminated by none of the filth on which it sheds itself, so the essence of the eternal and incorporeal light could be polluted by nothing which it assumed (Serm. xxxiv. 4)
In proof of this doctrine of the Incarnation Leo appeals to several classes of evidence, sometimes to the analogies of reason—why, he urges, cannot the divinity and humanity be one person, when soul and body in man form one person? (Ep. xxvi. 2); constantly to Scripture—the very source of heresy is that man will not labour "in the broad fields of Holy Scripture" ("in latitudine SS.," Ep. xxviii. i and 2); constantly to the creeds and the past of the church (for he hates novelty) it is the creed which introduces us to Scripture (Ep. cxxviii. 1); we need not blush to believe what apostles and those whom they taught, what martyrs and confessors believed (Epp. clxv. 9; clii.); but Leo very often and very characteristically appeals also to consequences, and looks at a doctrine in the light of the necessities of the church's life. What becomes of the salvation of our human nature if Christ have it not? How can He be the Head of the new race? How can He clothe our human nature with His divine? ("Caro enim Christi velamen est verbi, quo omnis qui ipsum integre confitetur induitur," Ep. lix. 4). What is the meaning of the Holy Communion of His Body and Blood, the very purpose of which is that, receiving the virtue of the heavenly food, we may pass into ("transeamus in") His flesh Who became our flesh? (Ep. lix. 2; cf. also Serm. xci. 3). What becomes of the resurrection and ascension; nay, what becomes of His mediation? How does He reconcile man to God if He have not the whole of humanity, except sin? (Ep. cxxiv. 6, 7, and Serm. xxv 5, etc.).
The Atonement.—Leo holds the view once prevalent, but now utterly abandoned, which may be stated out of his writings as follows. Man in his fallen state was in slavery to the devil, and, as by his own free will he had fallen, justly so. The devil had certain rights over him which he would retain unless that humanity which he had conquered could conquer him again. In redeeming man, God chose to overcome the devil rather by the rule of justice than of power. To this end He became Man. The Incarnation deceived the devil. He knew not with Whom he was matched. He saw a Child suffering the sorrows and pains of childhood; he saw Him grow by natural stages to manhood, and having had so many proofs that He was mortal He concluded that He was infected with the poison of original sin. So he set in force against Him, as though exercising a right upon sin-stained humanity, all methods and instruments of persecution, thinking that, if He, Whose virtues exceeded so far those of all saints, must yield to death and His merits availed not to deliver Him, he would be secure of every one else for ever. But in persecuting and slaying Christ, Whom was he slaying? One Who was man, but sinless, Who owed him nothing, and thus, by exacting the penalty of iniquity from Him in Whom he had found no fault, he went beyond his right. The covenant which bound man to the devil was thus broken. His injustice in demanding too much cancelled the whole debt of man due to him. Man was free. (Serm. xxii. 3, 4; lxix. 3; cf. xvi. 1, lxi. 4. The nails which pierced our Lord's hands and feet transfixed the devil with perpetual wounds, lxiv. 2, 3.) Thus, to effect our redemption, Christ must have been both man and God; and it was necessary that He should suffer and die by the operations of the devil; and His death has a value different in kind from that of all the saints (Serm. lxiv. 2, 3; lix. 1). On the cross of Christ the oblation of human nature was made by a saving victim (lv. 3). His death, the just for the unjust, was a price of infinite value (lvi. 3; lvii. 4). According to this theory, the price was paid to the devil and man was free; "redemptio aufert captivitatem et regeneratio mutat originem et fides justificat peccatorem" (xxii. 4). Nothing is said about—there is hardly clear room left for—an oblation to God. Elsewhere, however, Leo speaks of Christ as offering a "new and true sacrifice of reconciliation to His Father" (Serm. lix. 5; cf. Ep. cxxiv. 2, where the sacrifice is clearly conceived as offered to the Father. Cf. also Serm. lxiv. 2, 3).
The Doctrine of Grace.—Living, though Leo did, in a time when this doctrine was still in dispute, and mixed up, as he had been, in part of the dispute, we have little in his genuine works on the subject. He speaks of it indeed (Ep. i. 3) in orthodox terms. "The whole gift of God's works depends upon the previous operation of God ['omnis bonorum operum donatio, divina praeparatio est'], for no man is justified by virtue before he is [justified] by grace, which is to every man the beginning of righteousness, the fount of good, and the source of merit." Nothing in us, he implies, can antedate the operation of grace; all in us needs the salvation of Christ; but this grace of God which alone justifies was given, not for the first time, but in larger measure ("aucta non coepta") by Christ's birth, and this "sacrament of great holiness" (the Incarnation) was so powerful, even in its previous indications ("tam potens etiam in significationibus suis"), that they who hoped in the promise received it no less than they who accepted the gift" (Serm. xxii. 4). On this subject he often dwells; the Incarnation is the consummation of a previous presence and operation of the Son (Serm. xxv. 4). All through the O.T. men were justified by the same faith, and made part of the body of Christ by the same sacrament (Serm. xxx. 7; liv. 1). This same truth comes out in his sermons on Pentecost. There is perfect equality, he there says, in the Trinity. "It is eternal to the Father to be the Father of the co-eternal Son. It is eternal to the Son to be begotten of the Father out of all time. It is eternal to the Holy Spirit to be the Spirit of
