Gerrish's great book Grace and Gratitude is one I have owned for many years and only now begun to read. Oh well...
He gives a terrific account of Calvin's pastoral concern in the Institutes - something he learnt from Erasmus; but that in addition, as his work progressed, he was concerned to show the thematic (if not 'systematic')coherence of his theology. The doctrines are not isolated entities, but mutually conditioning of one another.
Hence Gerrish's study of Calvin's Eucharistic theology is a useful introduction (well, so far!) into Calvin's work as a whole.
What becomes clearer in the final edition of Calvin's Institutes is that the father's liberality and his children's answering gratitude, or lack of it, is not only the theme of the Lord's Supper but a fundamental theme, perhaps the most fundamental theme, of an entire systeme of theology. It conveys, as nothing else can, the heart of Calvin's perception of God, humanity, and the harmony between them that was lost by Adam and restored by Christ...Piety and its renewal as faith in Christ - that is the subject of Calvin's pietatis summa. The holy banquet is simply the liturgical enactment of the them of grace and gratitude that lies at the heart of Calvin's entire theology... (p. 20).
