Perhaps you will say, 'I see something else, how is it that you assert that I receive the Body of Christ?' And this is the point which remains for us to prove. And what evidence shall we make use of? Let us prove that this is not what nature made, but what the blessing consecrated, and the power of blessing is greater than that of nature, because by blessing nature itself is changed...The Lord Jesus Himself proclaims: 'This is My Body.' Before the blessing of the heavenly words another nature is spoken of, after the consecration the Body is signified. He Himself speaks of His Blood. Before the consecration it has another name, after it is called Blood. And you say, Amen, that is, It is true. Let the heart within confess what the mouth utters, let the soul feel what the voice speaks."
Ambrose,On the Mysteries,9:50(A.D. 390-391),in NPNF2,X:324-325
For more patristic quotes on Eucharist go here.
Or you could just think of Our Woman Flannery O'Connor, having endured the cool, jaded (dare we say) Collapsed Catholic ramblings of Mary McCarthy for an evening, responding to McCarthy's blow-off of the Eucharist by saying, in a self-described "shaky voice", "'Well, if it's a symbol, to hell with it.'.....That was all the defense I was capable of but I realize now that this is all I will ever be able to say about it, outside a story, except that it is the center of existence for me; all the rest is expendable.''
