Gelasius, bishop of Caesarea (d. before 401), is said by Photius to have composed an ecclesiastical history (Bibliotheca, Codex 89). He is traditionally called the first Nicene successor of Eusebius of Caesarea (but that honour should, probably, go to Philo of Carpasia). The work is also cited by the Anonymus ecclesiastical historian of Cyzicus (last quarter of the fifth century), the seventh-century Epitome of ecclesiastical histories, Theophanes, and in a couple of Byzantine saints’ Lives. The transmission is beset by problems. In Photius and many other witnesses Gelasius is identified with the Latin church historian Rufinus (certainly writing after Gelasius’ lifetime, c. 402–3) or he is stated to have translated Rufinus. Moreover, we have independent citations in Greek from the church history of Rufinus. In addition, the Anonymus of Cyzicus circulated under the name of Gelasius of Caesarea at the time of Photius, meaning that citations from the latter may be from the former. Finally, Photius thought that for stylistic reasons the author of the ecclesiastical history could not be identical to the one of the theological treatises ascribed to Gelasius of Caesarea. Such a complex transmission allows for various reconstructions, none of which is likely to command universal assent. With two collaborators, M. Wallraff, who has distinguished himself with important work on Socrates and Julius Africanus, now produces the first edition of the extant fragments in the prestigious GCS series. To the fragments of the ecclesiastical history, the team has added those of Gelasius’ dogmatic works, which have received little or no attention so far. They provide an accurate English translation, a copious introduction and notes, which focus mainly on the constitution of the text. The work is done meticulously, translations are clear and the notes are usually accurate. This new edition will be the first port of call for those interested in this still fairly marginal figure. Users should be aware that the present edition offers a reconstruction of the lost work and not an edition of fragments as commonly understood and therefore deviates in many aspects from common practice in the study of fragmentary Greek historians, as evidenced in the standard collections of F. Müller and F. Jacoby. Besides including passages that the sources nominally attribute to Gelasius, they add passages attributed on the basis of Quellenforschung. These are not distinguished from the first group of fragments, making it virtually impossible for the reader to distinguish the first group, which is the core group of fragments of which we can more or less be certain that they derive from Gelasius, from the second one, which is based on modern reconstructions of relations between different citing authorities. As Jacoby famously said, the certainty reached by Quellenforschung ‘is mostly overestimated’ and this is all the more true for a complicated transmission like that of Gelasius. I fear that the editors are somewhat too confident of their Quellenforschung, for it relies on an implicit yet questionable assumption, namely that later authorities citing Gelasius are fundamentally passive copyists and that hence minor deviations between different texts are sufficient to identify the use of a different source. Indeed, the fact that the authors say that to use the ‘stemmatic method’ (p. lviii) to establish the relationship between the citing authorities illustrates the point: by treating citing authorities as manuscripts, the assumption is that they stick as literally to the text that they cite as the copyist intends to do with the manuscript that he copies. Yet it is obvious from this edition itself that none of the citing authorities actually is such a slavish copyist. For example, in the discussion of Theodoret of Cyr, differences with Rufinus are suggested to derive from Gelasius, whilst Theodoret is well-known to rhetorically elaborate his sources. If the Anonymus of Cyzicus is repeatedly said to re-order and rework the material from Gelasius and his sources, the fact that he re-orders four documents that we find in Socrates is adduced as an argument that these documents must come from Gelasius – tacitly assuming that the Anonymus could not have re-ordered them himself (p. xlix). Editorial confidence is also visible in another way in which this edition deviates from common practice: when there are two or more witnesses to a fragment, the editors produce a composite text, that is, they combine elements from the different witnesses. In other editions of ancient fragmentary historians, such fragments are numbered a, b, c with the texts printed separately, allowing the reader to form his own judgement. The choice made here relies on the assumption that the relationship between the different citing authorities can be established without any doubt. Yet the transmission is too complex for that. For example, the Anonymus of Cyzicus circulated under the name of Gelasius of Caesarea at the time of Photius, which renders it possible that passages ascribed to Gelasius of Caesarea and identical to the Anonymus of Cyzicus derive in fact directly from the Anonymus (for example, F5 and F6). Many of the witnesses to Gelasius are also known to have used directly other supposed witnesses to Gelasius (BHG 185 and 1279 are cases in point), which renders cross-fertilisation between sources highly likely. The decision to deviate from standard practice in classical philology has an important consequence. The unsuspecting reader may not realise that a traditional edition of the fragments would count maybe 20 pages instead of the 255 pages in this edition – with the editors suggesting that they have been able to reconstruct most of Gelasius (p. lxxxiii). The methodological choices in this edition derive from its intention to prove that F. Winkelmann's reconstruction (Untersuchungen zur Kirchengeschichte des Gelasios von Kaisareia, Berlin 1966) is correct. His reconstruction is undoubtedly a possible one, but recent scholarship has suggested alternatives (P. Blaudeau, Alexandrie et Constantinople, Rome 2006, 500; J. Reidy, ‘The heirs of Eusebius’, unpubl. dissertation, St Louis 2015) that this edition would have done well to discuss.