John fisher's theology of justification, unlike that of Luther and the Reformers, left room for the sacraments to play an active part in the Christian life. For him, as for the Christian tradition since the earliest times, the eucharist was pre-eminent among the sacraments. A considerable body of theological speculation, as well as of devotional practice, had grown up around this sacrament, especially in the Middle Ages. It is therefore no surprise that the eucharist should have rapidly become one of the most bitterly contested issues of the Reformation. Nowhere was this more true than in England, where the eucharist probably provoked more debate between Catholics and Protestants than any other single question. Three of Fisher's polemical works deal largely with aspects of the eucharistic controversy. The Defensio Regiae Assertionis and the Sacri Sacerdotii Defensio defend the sacrifice of the mass and the concomitant doctrine of the sacrificing priesthood against Luther, and the De Veritate is a defence of the real presence in the eucharist against the Swiss Reformer Oecolampadius. These three books provide the framework of this chapter, which thus looks first at the mass, then at the priesthood and finally at the sacrament in itself. Since this analysis also amounts to a chronological approach, it affords us an opportunity to examine the development of Fisher's response to Reformed eucharistic doctrine. For the new challenges posed at successive stages of the debate elicited from him new responses in a process of development which again undermines the notion that he was an entirely conventional theologian.