Tertullian:
They thought His discourse was harsh and intolerable, supposing that He had really and literally enjoined on them to eat his flesh, He, with the view of ordering the state of salvation as a spiritual thing, set out with the principle, It is the spirit that quickens; and then added, The flesh profits nothing — meaning, of course, to the giving of life. He also goes on to explain what He would have us to understand by spirit: The words that I speak unto you, they are spirit, and they are life. In a like sense He had previously said: He that hears my words, and believes in Him that sent me, has everlasting life, and shall not come into condemnation, but shall pass from death unto life. Constituting, therefore, His word as the life-giving principle, because that word is spirit and life, He likewise called His flesh by the same appellation; because, too, the Word had become flesh, We ought therefore to desire Him in order that we may have life, and to devour Him with the ear, and to ruminate on Him with the understanding, and to digest Him by faith. (On the Resurrection of the Flesh 37)
Donald, this is a really disingenuous quotation as
Tertuallian is not even commenting about the Eucharist. He is defending the resurrection of the flesh from those who alleged that the flesh is unprofitable on the basis of Christ’s words in John 6. He is explaining that Christ was correcting the Jews’ notion that he was literally commanding cannibalism. Tertullian is not teaching Docetism or denying the Eucharist. When he says that we should “devour him with the ear” and “ruminate on him with understanding,” he is not denying the Eucharist anymore than he is denying the Incarnation.
This would be meaningful if Tertullian did not believe in the Eucharist, but it is a fact that he wrote about it elsewhere.
When He so earnestly expressed His desire to eat the passover, He considered it His own feast; for it would have been unworthy of God to desire to partake of what was not His own. Then, having taken the bread and given it to His disciples, He made it His own body, by saying, “This is my body,” that is, the figure of my body. A figure, however, there could not have been, unless there were first a veritable body. An empty thing, or phantom, is incapable of a figure. If, however, (as Marcion might say,) He pretended the bread was His body, because He lacked the truth of bodily substance, it follows that He must have given bread for us. It would contribute very well to the support of Marcion’s theory of a phantom body, that bread should have been crucified! But why call His body bread, and not rather (some other edible thing, say) a melon, which Marcion must have had in lieu of a heart! He did not understand how ancient was this figure of the body of Christ, who said Himself by Jeremiah: “I was like a lamb or an ox that is brought to the slaughter, and I knew not that they devised a device against me, saying, Let us cast the tree upon His bread,” which means, of course, the cross upon His body. And thus, casting light, as He always did, upon the ancient prophecies, He declared plainly enough what He meant by the bread, when He called the bread His own body. He likewise, when mentioning the cup and making the new testament to be sealed “in His blood,” affirms the reality of His body. For no blood can belong to a body which is not a body of flesh. If any sort of body were presented to our view, which is not one of flesh, not being fleshly, it would not possess blood. Thus, from the evidence of the flesh, we get a proof of the body, and a proof of the flesh from the evidence of the blood. In order, however, that you may discover how anciently wine is used as a figure for blood, turn to Isaiah, who asks, “Who is this that comes from Edom, from Bosor with garments dyed in red, so glorious in His apparel, in the greatness of his might? Why are your garments red, and your raiment as his who comes from the treading of the full winepress?” The prophetic Spirit contemplates the Lord as if He were already on His way to His passion, clad in His fleshly nature; and as He was to suffer therein, He represents the bleeding condition of His flesh under the metaphor of garments dyed in red, as if reddened in the treading and crushing process of the wine-press, from which the labourers descend reddened with the wine-juice, like men stained in blood. Much more clearly still does the book of Genesis foretell this, when (in the blessing of Judah, out of whose tribe Christ was to come according to the flesh) it even then delineated Christ in the person of that patriarch, saying, “He washed His garments in wine, and His clothes in the blood of grapes” — in His garments and clothes the prophecy pointed out his flesh, and His blood in the wine. Thus did He now consecrate His blood in wine, who then (by the patriarch) used the figure of wine to describe His blood.
(Against Marcion IV.40)
Look at the part I underlined. Tertullian says that if Marcion is correct and Jesus did not have a true body, then it follows that Jesus gave bread for us. However, he says this as if it were an unreasonable conclusion. WHy is this? Because he identifies the bread with the crucified body of Christ. If Tertullian believed in a purely symbolic interpretation, then it would not follow that bread was crucified on the cross. After all, bread could symbolize something that didn’t exist, but it could not be something that didn’t exist. On the contrary, Tertullian identifies the Eucharist with the crucified body of Christ so it follows that if the Eucharistic bread is not a figure of anything more than bread, then only bread was crucified.