"Filius dei filius hominis factus," "it is one and the same Jesus Christ, not a Jesus and a Christ, nor a mere temporary union of an aeon and a man, but one and the same person, who created the world, was born, suffered, and ascended"--this along with the dogma of God the Creator is the cardinal doctrine of Irenaeus:[577] "Jesus Christ truly man and truly God" ("Jesus Christus, vere homo, vere deus").[578] It is only the Church that adheres to this doctrine, for "none of the heretics hold the opinion that the Word of God became flesh" ("secundum nullam sententiam haereticorum verbum dei caro factum est").[579] What therefore has to be shown is (1) that Jesus Christ is really the Word of God, i.e., is God, (2) that this Word really became man and (3) that the incarnate Word is an inseparable unity. Irenaeus maintains the first statement as well against the "Ebionites" as against the Valentinians who thought that Christ's advent was the descent of one of the many aeons. In opposition to the Ebionites he emphasises the distinction between natural and adopted Sonship, appeals to the Old Testament testimony in favour of the divinity of Christ,[580] and moreover argues that we would still be in the bondage of the old disobedience, if Jesus Christ had only been a man.[581] In this connection he also discussed the birth from the virgin.[582] He not only proved it from prophecy, but his recapitulation theory also suggested to him a parallel between Adam and Eve on the one hand and Christ and Mary on the other, which included the birth from the virgin.[583] He argues in opposition to the Valentinians that it was really the eternal Word of God himself, who was always with God and always present to the human race, that descended.[584] He who became man was not a being foreign to the world--this is said in opposition to Marcion--but the Lord of the world and humanity, the Son of God, and none other. The reality of the body of Christ, i.e., the essential identity of the humanity of Christ with our own, was continually emphasised by Irenaeus, and he views the whole work of salvation as dependent on this identity.[585] In the latter he also includes the fact that Jesus must have passed through and been subjected to all the conditions of a complete human life from birth to old age and death.[586] Jesus Christ is therefore the Son of God who has really become the Son of man; and these are not two Christs but one, in whom the Logos is permanently united with humanity.[587] Irenaeus called this union "union of the Word of God with the creature" ("adunitio verbi dei ad plasma")[588] and "blending and communion of God and man" ("commixtio et communio dei et hominis")[589] without thereby describing it any more clearly.[590] He views it as perfect, for, _as a rule_, he will not listen to any separation of what was done by the man Jesus and by God the Word.[591] The explicit formula of two substances or natures in