To this end I think it is very important to note the changes that occur in Against Heresies's report about the adoptionist beliefs of gnostics when compared to the original Irenaean lecture preserved by Tertullian in Against Valentinians. In the original report the man 'Christ' is baptized into the heavenly hypostasis Jesus:
Now I continue with what they say about Christ on whom they graft Jesus--with the same liberty as when they stuff the spirit-like seed in him along with the soul-like breath. They make him a mash of inventions of both Men and gods: the Demiurge also has his own Christ, his natural son (consequently soul-like), produced from himself, preached by the prophets. His nature must be decided by prepositions: specifically, he was produced through a virgin, not from a virgin, because he came into existence carried in a virgin in a transportational, not a generational, sense. He came through her, not from her; he experienced her not as a mother but as a conveyance. Upon this Christ, then, in the sacrament of baptism, Jesus descended in the form of a dove. [Against Valentinians 28]
Compare the heavenly Jesus grafted on to the earthly Christ with the parallel material in Against Heresies which has been clearly corrupted:
There are also some who maintain that he [i.e. the Demiurge] also produced Christ as his own proper son, but of an animal nature, and that mention was made of him by the prophets. This Christ passed through Mary just as water flows through a tube; and there descended upon him [Jesus] in the form of a dove it the time of his baptism, that Saviour who belonged to the Pleroma, and was formed by the combined efforts of all its inhabit ants. In him there existed also that spiritual seed which proceeded from Achamoth. They hold, accordingly, that our Lord, while preserving the type of the first-begotten and primary tetrad, was compounded of these four substances,--of that which is spiritual, in so far as He was from Achamoth; of that which is animal, as being from the Demiurge by a special dispensation, inasmuch as He was formed [corporeally] with unspeakable skill; and of the Saviour, as respects that dove which descended upon Him. He also continued free from all suffering, since indeed it was not possible that He should suffer who was at once incomprehensible and invisible.
And for this reason the Spirit of Christ, who had been placed within Him, was taken away when He was brought before Pilate. They maintain, further, that not even the seed which He had received from the mother [Achamoth] was subject to suffering; for it, too, was impassible, as being spiritual, and invisible even to the Demiurge himself. It follows, then, according to them, that the animal Christ, and that which had been formed mysteriously by a special dispensation, underwent suffering, that the mother might exhibit through him a type of the Christ above ... In like manner, they hold that Jesus uttered some things under the influence of the Saviour, others under that of the mother, and others still under that of the Demiurge, as we shall show further on in our work. [Irenaeus AH 1.7.2,3]
and again in the related section on the Marcosians we hear of some reports which identify the sect as referencing a 'supercelestial Jesus' coming down like a dove on an 'earthly Jesus':
Thus, then, you have a clear statement of their opinion as to the origin of the supercelestial Jesus. Wherefore, also, the alphabet of the Greeks contains eight Monads, eight Decads, and eight Hecatads, which present the number eight hundred and eighty-eight, that is, Jesus, who is formed of all numbers; and on this account He is called Alpha and Omega, indicating His origin from all ... [a]nd thus, by a special dispensation, there was generated by Him, through Mary, that man, whom, as He passed through the womb, the Father of all chose to [obtain] the knowledge of Himself by means of the Word. And on His coming to the water [of baptism], there descended on Him, in the form of a dove, that Being who had formerly ascended on high, and completed the twelfth number, in whom there existed the seed of those who were produced contemporaneously with Himself, and who descended and ascended along with Him. Moreover, he maintains that power which descended was the seed of the Father, which had in itself both the Father and the Son, as well as that power of Sige which is known by means of them, but cannot be expressed in language, and also all the AEons. And this was that Spirit who spoke by the mouth of Jesus, and who confessed that He was the son of Man as well as revealed the Father, and who, having descended into Jesus, was made one with Him. And he says that the Saviour formed by special dispensation did indeed destroy death, but that Christ made known the Father. He maintains, therefore, that Jesus is the name of that man formed by a special dispensation, and that He was formed after the likeness and form of that [heavenly] Anthropos, who was about to descend upon Him. After He had received that AEon, He possessed Anthropos himself, and Loges himself, and Pater, and Arrhetus, and Sige, and Aletheia, and Ecclesia, and Zoe. [ibid 1.15.2,3]
or in some cases the very same report about the very same sect has a 'heavenly Christ' descending upon an 'earthly Jesus':
For the baptism instituted by the visible Jesus was for the remission of sins, but the redemption brought in by that Christ who descended upon Him, was for perfection; and they allege that the former is animal, but the latter spiritual. And the baptism of John was proclaimed with a view to repentance, but the redemption by Jesus was brought in for the sake of perfection [ibid 1.21.1,2]
Yet it is impossible that the same sect has two different accounts of whether 'Christ' or 'Jesus' is heavenly or earthly. The obvious answer - the answer which solves the riddle of adoptionism and brings early Christianity back in line with the so-called 'Secret Gospel' of Mark - is that Christ was clearly the earthly being and Jesus the heavenly one. It is only our inherited presuppositions that fail to recognize that Tertullian is citing from an earlier version of the original lecture by Irenaeus later incorporated into Against Heresies.
