theologian. He entered the monastery of Corbie c.825. His De Corpore et Sanguine Domini (843) was a reaction to the realism of Paschasius Radbertus' earlier treatise on the Eucharist. In his De Praedestinatione (849–50), he clarified the patristic basis for Gottschalk's belief in double predestination to good or evil. His Contra Graecorum Opposita (c.867) is a reply to Photius's criticism of the W. Church; in it he defends the Double Procession of the Holy Spirit. In the 11th cent. his Eucharistic treatise was seen as incompatible with a change in the substance of the Bread and Wine and condemned in 1050. Only at the time of the Reformation was it much read; it was a major source for N. Ridley's formulations of Eucharistic doctrine.