In book I, chapter six of his Paedagogus (The Instructor of Children), St. Clement affirms that the Eucharist is both symbolic and the Real Presence, i.e., the body and blood, soul, and divinity of Jesus Christ. First, he discusses its symbolic value:
Elsewhere the Lord, in the Gospel according to John, brought this out by symbols, when he said: Eat my flesh, and drink my blood; John 6:34 describing distinctly by metaphor the drinkable properties of faith and the promise, by means of which the Church, like a human being consisting of many members, is refreshed and grows, is welded together and compacted of both — of faith, which is the body, and of hope, which is the soul; as also the Lord of flesh and blood.
Later in the same chapter, he affirms the Real Presence:
Eat my flesh, he says, and drink my blood (John 6:53-5). Such is the suitable food which the Lord ministers, and he offers his flesh and pours forth his blood, and nothing is wanting for the children’s growth. O, amazing mystery! We are enjoined to cast off the old and carnal corruption, as also the old nutriment, receiving in exchange another new regimen, that of Christ, receiving him if we can, to hide him within; and that, enshrining the Savior in our souls, we may correct the affections of our flesh.
If the Eucharist were purely a symbol, it wouldn’t be an “amazing mystery.” The Real Presence is further affirmed by St. Clement’s assertion that we hide Christ within us in receiving the Eucharist, “enshrining the Savior in our souls.” This can’t happen if the Eucharist were merely bread and wine and thus only a symbol of his body and blood.