The excellent report by H.-R. Schwyzer in his long article on Plotinus in R.-E. (Bd. XLI (1951), col. 477–81), presents the reader with a picture of the present state of research concerning Ammonius, while giving a critique of previous discussions. A significant feature of the situation is this: simultaneously with the endeavour to obtain a clear picture of Ammonius's doctrine from the reports in Nemesius of Emesa and Hierocles (Photius, Bibl. cod. 214 and 251)—reports whose upper and lower limits are controversial—a new and fruitful attempt has been made to work back to Ammonius as the common source behind numerous concordances between Plotinus and Origen. Following the lead of René Cadiou, who, in his epoch-making work La jeunesse d'Origène (Paris, 1935), demonstrated the importance of Ammonius for the development of the theology of Origen, de Jong has given a convenient conspectus of the parallels between Plotinus and Origen (Plotinus of Ammonius Saccas, Leiden, 1941). But this gives rise to some problems of general procedure. What justification is there for Schwyzer's assertion (op. cit. 480. 65) that ‘it is a priori improbable that Plotinus would have studied the writings of Origen’? This depends upon the presupposition that Christianity, and in particular its theology, during the years of Plotinus's studies at Alexandria, was of far too slight importance, intensive or extensive, to have had any influence upon a man of the spiritual calibre of Plotinus.