This article examines how the historian deals with ‘information’ broadly conceived, especially its acquisition, retention and loss. Ammianus details a complex interplay between those who control information and those who must work with an information deficit. Just as this dialogue plays out within the text, however, so too does it with respect to the author's methodology, which dances between the poles of incomplete and complete information depending on circumstance. Ammianus thus becomes an author as hard to pin down as many of his characters, by turns the omniscient narrator and the dumbfounded participant.

This article identifies a double allusion to the tragic characters of Phaedra and Eriphyle in Amm. Marc. 14.1.3 and considers its possible meanings. In combination, these allusions evoke the double nature of the story of Eriphyle, therefore functioning as a reference to the double nature of Caesar Gallus’ depiction in Ammianus. The double allusion consequently forms part of Ammianus’ tragic style throughout Book 14. Having identified the presence of this double allusion, the article illuminates its possible meaning by connecting Ammianus’ passage to the Virgilian rewriting of the description of Eriphyle in Homer.

The Res Gestae of Ammianus Marcellinus poses numerous structural puzzles for the historian, among them the anomalous final book, numbered 31 in the manuscript tradition. This book, which treats the Gothic rebellion of a.d. 376–378 and the campaign of Adrianople, is loosely connected to the other extant books, which conclude with events of a.d. 375. The present article argues that Book 31 was in origin a separate monograph, drafted in Greek at Antioch in the aftermath of the Roman defeat at Adrianople. Perhaps modelled on the Scythica of Dexippus, its contents reflect the Antiochene and Constantinopolitan polemic of its moment. For reasons that must remain speculative, Ammianus later translated his work into Latin and appended it to a finished draft of the Res Gestae.