The work of L. Caecilius Firmianus Lactantius (c. A. D. 245-325) has been assessed from a variety of perspectives. The author has been judged as a theologian, a philosopher, a rhetorician, an apologist and, most negatively, as a patchworker of writ ten sources. This dissertation argues that a satisfactory appreciation of Lactantius as an author cannot be provided from any of the above bases but only by commencing from a study of the purpose and plan of his works in relation to his self-understanding as a writer. I argue that such an approach reveals that Lactantius regarded himself as the Christian Cicero, the way that he has sometimes been described by commentators, and� that this self-understanding determines the whole character of his work. Chapter 1 argues that such a self-understanding is suggested by Lactantius' references to Cicero and to himself in relation to Cicero . The rest of the dissertation sets out to add proof to the suggestion. Chapters 2-4 reassess the seven-book Diuinae Institutiones, the De Opificio Dei, and the De Ira Dei . It is argued that the purpose of these treatises deliberately parallels that of Cicero's philosophical works and that each volume, with one important exception, has a close and intended relationship to a Ciceronian dialogue. Lactantius intends to show that because of his Christian faith his work will succeed where Tullius' failed. Chapters 5-7 examine the consequences of the earlier chapters' arguments for our assessment of Lactantius' place in the history of ideas. This examination is carried out by means of a case study, an investigation into the author's relationship to the major Hell~nistic schools of philosophy - the Epicureans, the Stoics and the New Academy. These chapters confirm that Lactantius saw himself as the Christian Cicero and they show that he is less important as a source for philosophical detail than he is for what he reveals to us about the place of Hellenistic thought in educated Latin society in the late Roman period. I argue that Lactantius' work has sometimes been misinterpreted and misused as a source, for example in relation to Carneades' visit to Rome. Against Lactantius' cri ties I maintain that his writing succeeds in its objectives . Steeped in the Latin classical authors, above all Cicero, he uses these skilfully and acutely in the contemporary fight between the Church and its opponents for the minds of the educated Roman classes.