One has to be impressed—at least I am—by St Irenaeus’s invocation of the Eucharist to support the catholic view of the Incarnation:
But vain in every respect are they who despise the entire dispensation of God, and disallow the salvation of the flesh, and treat with contempt its regeneration, maintaining that it is not capable of incorruption. But if this indeed do not attain salvation, then neither did the Lord redeem us with His blood, nor is the cup of the Eucharist the communion of His blood, nor the bread which we break the communion of His body. For blood can only come from veins and flesh, and whatsoever else makes up the substance of man, such as the Word of God was actually made. By His own blood he redeemed us, as also His apostle declares, “In whom we have redemption through His blood, even the remission of sins.” And as we are His members, we are also nourished by means of the creation (and He Himself grants the creation to us, for He causes His sun to rise, and sends rain when He wills). He has acknowledged the cup (which is a part of the creation) as His own blood, from which He bedews our blood; and the bread (also a part of the creation) He has established as His own body, from which He gives increase to our bodies.
When, therefore, the mingled cup and the manufactured bread receives the Word of God, and the Eucharist of the blood and the body of Christ is made, from which things the substance of our flesh is increased and supported, how can they affirm that the flesh is incapable of receiving the gift of God, which is life eternal, which [flesh] is nourished from the body and blood of the Lord, and is a member of Him? — even as the blessed Paul declares in his Epistle to the Ephesians, that “we are members of His body, of His flesh, and of His bones.” He does not speak these words of some spiritual and invisible man, for a spirit has not bones nor flesh; but [he refers to] that dispensation [by which the Lord became] an actual man, consisting of flesh, and nerves, and bones, — that [flesh] which is nourished by the cup which is His blood, and receives increase from the bread which is His body. And just as a cutting from the vine planted in the ground fructifies in its season, or as a corn of wheat falling into the earth and becoming decomposed, rises with manifold increase by the Spirit of God, who contains all things, and then, through the wisdom of God, serves for the use of men, and having received the Word of God, becomes the Eucharist, which is the body and blood of Christ; so also our bodies, being nourished by it, and deposited in the earth, and suffering decomposition there, shall rise at their appointed time, the Word of God granting them resurrection to the glory of God, even the Father, who freely gives to this mortal immortality, and to this corruptible incorruption, because the strength of God is made perfect in weakness. (AH 5.2.2-3)
A member of a Christian-gnostic community might not be impressed by this argument, but an orthodox Christian probably should be, as it appeals to the central and defining act of Christian worship. We know that God sanctifies the material because he gives to us the Body and Blood of Christ to us every Sunday. It’s all of a piece—the good world God has created, the assumption of human nature by the Son, the shedding of his blood on the Cross, the glorification of the body in the resurrection, the Holy Gifts, the recreation of the cosmos at the Second Coming.