Book 4 of 4 - External Means by which God Invites Us into the Society of Christ and Holds Us Therein
Chapter 17 - The Lord's Supper; what it brings to us
4-7 - Promise sealed - partaking of Christ's body a mystery
4. The point isn't just to offer us Christ, but to confirm the truth that He nourishes us. He is our bread (John 6:48, 50, 55-6), not because He is offered at the Supper, but because of what He did at the cross (1 Pet 3:22) and resurrection (1 Cor 15:53-54).
5. Applying these events to our lives is done by Gospel preaching, "but more clearly through the Sacred Supper." We should neither separate the spiritual reality of the Sacrament from the symbols "by too little regard for the signs," nor obscure the reality "by extolling [the symbols] immoderately." The Supper shows that partaking of Christ is more than "mere knowledge:" we don't just see the bread, we eat it. Our spiritual life is fed by union with Christ, not just knowing about Him.
6. Augustine and Chrysostom said this, too: it's okay to say that the physical eating is like spiritual faith, as long as that faith is more than "mere imagining" or seeing, but involves union with and partaking of Christ.
7. We don't understand the Supper fully, but something is more is going on than partaking of the Spirit only, "omitting [Christ's] flesh and blood." That error of omission isn't as great as Rome's transubstantiation nonsense, though. "My mind is conquered and overwhelmed by the greatness of the thing [meaning of the Lord's Supper]".