At one point, however, Calvin does more than summarise. He goes, we believe, beyond earlier positions (at least generally understood today), in a direction which not only marks him off clearly from the position of Zwingli and Bullinger but also might have provided the Maulbronner disputation with a more auspicious point of departure, if not with a formula concordiae. Dealing with II Sam. vi. 2 (‘Dieu des armees habitant entre les cherubins’) Calvin applies the text to Baptism and the Eucharist: ‘We should not take these signs as mere visible things, symbols to nourish our spiritual senses, but we are to know that God there unites his power and his truth: both the res and the effectus are there with the symbol; one must not separate what God has joined together.’ If we are right in concluding that with the symbol or sign (sacramentum tantum) not only the visible element but also the res sacramenti or effectus is given, a manductio oralis seems to be unavoidably implied. Christ ‘habite en nous par foy’. To receive him in bread and wine, however, is not the effectus fidei but the effectus sacramenti, inseperably attached to the sacrament by God. The demarcation line between the objective act of God and the subjective act of faith runs between manductio and inhabitatio, not between exhibitio and receptio as the younger Calvin, the Pfaltzer theologians at Maulronn and – we may add- all those who later were to claim Calvin’s authority have taught.
~Heiko Oberman The Dawn of the Reformation pg. 241-242