For there was heresy to be combated; viz., the heresy of the scholastic theologian Berengar of Tours, who had attacked the doctrine of the transubstantiation of the bread and the wine of the Eucharist into the body and blood of Christ.  Lanfranc, Archbishop of Canterbury, one of the most brilliant of the Middle Age theologians, felt impelled to reply to Berengar, who had been his personal friend; and he did so in the ’Liber Scintillarum,’ which was a vigorous, indeed a violent, defense of the doctrine denied by Berengar.  Berengar died in 1088; but he left a considerable body of followers.  The heretics were anathematized by the Second Lateran Ecumenical Council held in Rome in 1139.  Again, in 1215, the Fourth Lateran Council declared transubstantiation to be an article of faith, and in 1264 a special holy day, Corpus Christi,—­viz., the first Thursday after Trinity Sunday,—­was set apart to give an annual public manifestation of the belief of the Church in the doctrine of the Eucharist.

But when the Fourth Lateran Ecumenical Council met in 1215, the transformation of the Arthurian legend by means of its association with the legend of the Holy Grail was already complete, and the transformed legend, now become a defender of the faith, was engrossing the imagination of Europe.  The subsequent influence of the legend was doubtless to some extent associated with the discussions which continually came up anew respecting the meaning of the doctrine of the Eucharist; for it was not until the Council of Trent (1545-63) that the doctrine was finally and authoritatively defined.  In the mean time there was interminable discussion respecting the nature of this “real presence,” respecting transubstantiation and consubstantiation and impanation, respecting the actual presence of the body and blood of Christ under the appearance of the bread and wine, or the presence of the body and blood together with the bread and wine.  The professor of philosophy in the University of Oxford, who passes daily through Logic Lane, has said that there the followers of Duns Scotus and Thomas Aquinas were wont to come to blows in the eagerness of their discussion respecting the proper definition of the doctrine.  Nor was the doctrine without interest to the Reformers.  Luther and Zwingli held opposing views, and Calvin was involved in a long dispute concerning the doctrine, which resulted in the division of the evangelical body into the two parties of the Lutherans and the Reformed.  Doubtless the connection between the Arthurian legend and the doctrine of the Divine Presence was not without influence on the unparalleled spread of the legend in the closing decades of the twelfth century, and on its prominence in the centuries following.