Though all the divine utterances exhort us, dearly beloved, to "rejoice in the Lord always(1) ," yet to-day we are no doubt incited to a full spiritual joy, when the mystery of the Lord's nativity is shining brightly upon us(2) , so that we may have recourse to that unutterable condescension of the Divine Mercy, whereby the Creator of men deigned to become man, and be found ourselves in His nature whom we worship in ours. For God the Son of God, the only-begotten of the eternal and not-begotten Father, remaining eternal "in the form of God," and unchangeably and without time(3) possessing the property of being no way different to the Father He received "the form of a slave" without loss of His own majesty, that He might advance us to His state and not lower Himself to ours. Hence both natures abiding in possession of their own properties such unity is the result of the union that whatever of Godhead is there is inseparable from the manhood: and whatever of manhood, is indivisible from the Godhead.
In celebrating therefore the birthday of our Lord and Saviour, dearly beloved, let us entertain pure thoughts of the blessed Virgin's child-bearing, so as to believe that at no moment of time was the power of the Word wanting to the flesh and soul which she conceived, and that the temple of Christ's body did not previously receive its form and soul that its Inhabitant might come and take possession but through Himself and in Himself was the beginning given to the New Man, so that in the one Son of God and Man there might be Godhead without a mother, and Manhood without a Father. For her virginity fecundated by the Holy Spirit at one and the same time brought forth without trace of corruption both the offspring and the Maker of her race. Hence also the same Lord, as the Evangelist relates, asked of the Jews whose son they had learnt Christ to be on the authority of the Scriptures, and when they replied that the tradition was He would come of David's seed, "How," saith He, "doth David in the Spirit call Him Lord, saying, the Lord said to my Lord: sit thou on My right hand till I place thy enemies as the footstool of thy feet(4) ?" And the Jews could not solve the question put, because they did not understand that in the one Christ both the stock of David and the Divine nature were there prophesied.
But the majesty of the Son of God in which He is equal with the Father in its garb of a slave's humility feared no diminution, required no augmentation: and the very effect of His mercy which He expended on the restitution of man, He was able to bring about solely by the power of His Godhead; so as to rescue the creature that was made in the image of God from the yoke of his cruel oppressor. But because the devil had not shown himself so violent in his attack on the first man as to bring him over to his side without the consent of His free will, man's voluntary sin and hostile desires had to be destroyed in such wise that the standard of justice should not stand in the way of the gift of Grace. And therefore in the general ruin of the entire human race there was but one remedy in the secret of the Divine plan which could succour the fallen, and that was that one of the sons of Adam should be born free and innocent of original transgression, to prevail for the rest both by His example and His merits. Still further, because this was not permitted by natural generation, and because there could be no offspring from our faulty stock without seed, of which the Scripture saith, "Who can make a clean thing conceived of an unclean seed? is it not Thou who art alone(5) ?" David's Lord was made David's Son, and from the fruit of the promised branch(6) sprang. One without fault, the twofold nature coining together into one Person, that by one and the same conception and birth might spring our Lord Jesus Christ, in Whom was present both true Godhead for the performance of mighty works and true Manhood for the endurance of sufferings.
The catholic Faith then, dearly beloved, may scorn the errors of the heretics that bark against it, who, deceived by the vanity of worldly wisdom, have forsaken the Gospel of Truth, and being unable to understand the Incarnation of the Word, have constructed for themselves out of the source of enlighten-merit occasion of blindness. For after investigating almost all false believers' opinions, even those which presume to deny the Holy Spirit, we come to the conclusion that hardly any one has gone astray, unless he has refused to believe the reality of the two natures in Christ under the confession of one Person. For some have ascribed to the Lord only manhood(7) , others only Deity(8) . Some have said that, though there was in the true Godhead, His flesh was unreal(9) . Others have acknowledged that He took true flesh but say that He had not the nature of God the Father; and by assigning to His Godhead what belonged to His human substance, have made for themselves a greater and a lesser God, although there can be in true Godhead no grades: seeing that whatever is less than God, is not God(10) . Others recognizing that there is no difference between Father and Son, because they could not understand unity of Godhead except in unity of Person, have maintained that the Father is the same as the Son(11) : so that to be born and nursed, to suffer and die, to be buried and rise again, belonged to the same Father who sustained throughout the Person of both Man and the Word. Certain have thought that our Lord Jesus Christ had a body not of our substance but assumed from higher and subtler elements(12) : whereas certain others have considered that in the flesh of Christ there was no human soul, but that the Godhead of the Word Itself fulfilled the part of soul(13) . But their unwise assertion passes into this form that, though they acknowledge the existence of a soul in the Lord, yet they say it was devoid of mind, because the Godhead of Itself was sufficient for all purposes of reason to the Man as well as to the God in Christ. Lastly the same people have dared to assert that a certain portion of the Word was turned into Flesh, so that in the manifold varieties of this one dogma, not only the nature of the flesh and of the soul but also the essence of the Word Itself is dissolved.
There are many other astounding falsehoods also which we must not weary your ears, beloved, with enumerating. But after all these various impieties, which are closely connected by the relationship that exists between one form of blasphemy and another, we call your devout attention to the avoiding of these two errors in particular: one of which, with Nestorius for its author, some time ago attempted to gainground, but ineffectually; the other, which is equally damnable, has more recently sprung up with Eutyches as its propounder. The former dared to maintain that the blessed Virgin Mary was the mother of Christ's manhood only, so that in her conception and childbearing no union might be believed to have taken place of the Word and the Flesh: because the Son of God did not Himself become Son of Man, but of His mere condescension linked Himself with created man. This can in no wise be tolerated by catholic ears, which are so imbued with the gospel of Truth that they know of a surety there is no hope of salvation for mankind unless He were Himself the Son of the Virgin who was His mother's Creator. On the other hand this blasphemous propounder of more recent profanity has confessed the union of the two Natures in Christ, but has maintained that the effect of this very union is that of the two one remained while the substance of the other no longer existed, which of course could not have been brought to an end except by either destruction or separation(14) . But this is so opposed to sound faith that it cannot be entertained without loss of one's Christian name. For if the Incarnation of the Word is the uniting of the Divine and human natures, but by the very fact of their coming together that which was twofold became single, it was only the Godhead that was born of the Virgin's womb, and went through the deceptive appearance of receiving nourishment and bodily growth: and to pass over all the changes of the human state, it was only the Godhead that was crucified, dead, and buried: so that according to those who thus think, there is no reason to hope for the resurrection, and Christ is not "the first-begotten from the dead(15) ;" because He was not One who ought to have been raised again, if He had not been One who could be slain.
Keep far from your hearts, dearly beloved, the poisonous lies of the devil's inspirations, and knowing that the eternal Godhead of the Son underwent no growth while with the Father, be wise and consider that to the same nature to which it was said in Adam, "Thou art earth, and unto earth shall thou go(16) ," it is said in Christ, "sit Thou on My right hand(17) ." According to that Nature, whereby Christ is equal to the Father, the Only-begotten was never inferior to the sublimity of the Father; nor was the glory which He had with the Father a temporal possession; for He is on the very right hand of the Father, of which it is said in Exodus, "Thy right hand, O Lord, is glorified in power(18) ;" and in Isaiah, "Lord, who hath believed our report? and the arm of the Lord, to whom is it revealed(19) ?" The man, therefore, assumed into the Son of God, was in such wise received into the unity of Christ's Person from His very commencement in the body, that without the Godhead He was not conceived, without the Godhead He was not brought forth, without the Godhead He was not nursed. It was the same Person in the wondrous acts, and in the endurance of insults; through His human weakness crucified, dead and buried: through His Divine power, being raised the third day, He ascended to the heavens, sat down at the right hand of the Father, and in His nature as man received from the Father that which in His nature as God He Himself also gave(20) .
Meditate, dearly beloved on these things with devout hearts, and be always mindful of the apostle's injunction, who admonishes all men, saying, "See lest any one deceive you through philosophy and vain deceit according to the tradition of men, and not according to Christ; for in Him dwelleth all the fulness of the Godhead bodily, and ye have been filled in Him(21) ." He said not "spiritually" but "bodily," that we may understand the substance of flesh to be real, where there is the dwelling in the body of the fulness of the Godhead: wherewith, of course, the whole Church is also filled, which, clinging to the Head, is the body of Christ; who liveth and reigneth with the Father and the Holy Ghost, God for ever and ever. Amen.