In a section full of interesting observations, Augustine has this to say about the life-giving principle of Christ:
The Principle is neither the flesh nor the human soul in Christ but the Word by which all things were made. The flesh, therefore, does not by its own virtue purify, but by virtue of the Word by which it was assumed, when “the Word became flesh and dwelt among us.” For speaking mystically of eating His flesh, when those who did not understand Him were offended and went away, saying, “This is an hard saying, who can hear it?” He answered to the rest who remained, “It is the Spirit that quickeneth; the flesh profiteth nothing.” The Principle, therefore, having assumed a human soul and flesh, cleanses the soul and flesh of believers. (City of God 10.24)
Not even the flesh of Christ gives us new life but is only an instrument in conveying the eternal Word to us. The editor of this volume informs us in a note that “principle” is used to mean “beginning,” and so it is the divine nature and role of the Logos as eternal originator which is in view.
And (perhaps it is too-obvious to point out) this also reminds us that everyone reads John 6 figuratively.