[3] The name Historia Augusta originated with Isaac Casaubon, who produced a critical edition in 1603, working from a complex manuscript tradition with a number of variant versions.

[4] The title as recorded on the Codex Palatinus manuscript, written in the 9th century, is Vitae Diversorum Principum et Tyrannorum a Divo Hadriano usque ad Numerianum Diversis compositae ("The Lives of various Emperors and Tyrants from the Divine Hadrian to Numerian by Various Authors").

For nearly 300 years after Casaubon's edition, though much of the Historia Augusta was treated with some scepticism, it was used by historians as an authentic source – Edward Gibbon used it extensively in the first volume of the Decline and Fall of the Roman Empire.

[11] However, "in modern times most scholars read the work as a piece of deliberate mystification written much later than its purported date, however the fundamentalist view still has distinguished support.

[24] Hermann Peter, editor of the Historia Augusta and of the Historicorum Romanorum reliquiae, proposed a date of 330 for when the work was written, based upon an analysis of style and language.

[26] In the 1960s and 1970s, Dessau's original arguments received powerful restatement and expansion from Sir Ronald Syme, who devoted three books to the subject and was prepared to date the writing of the work closely in the region of AD 395.

[36] Other opinions included H Stern's, who postulated that the History was composed by a team of writers during the reign of Constantius II after the defeat of Magnentius on behalf of the senatorial aristocracy who had supported the usurper.

[42] They share much idiosyncratic content and similar language, with particular focus on women, wine and military discipline, and were fixated on poor-quality plays on words ascribing personality traits to certain emperors, for instance Verus was truthful, while Severus was a severe individual.

[50] Thus among the biographies of 2nd-century and early 3rd-century figures are included Hadrian's heir Aelius Caesar, and the usurpers Avidius Cassius, Pescennius Niger and Clodius Albinus, Caracalla's brother Geta and Macrinus' son Diadumenianus.

The biography of Marcus Aurelius' colleague Lucius Verus, which Mommsen thought 'secondary', is rich in apparently reliable information and has been vindicated by Syme as belonging to the 'primary' series.

He still makes use of some recognized sources – Herodian up to 238, and probably Dexippus in the later books, for the entire imperial period the Enmannsche Kaisergeschichte as well as Aurelius Victor, Eutropius, Ammianus Marcellinus and Jerome – but the biographies are increasingly tracts of invention in which occasional nuggets of fact are embedded.

[57] Interpretations of the purpose of the History also vary considerably, some considering it a work of fiction or satire intended to entertain (perhaps in the vein of 1066 and All That), others viewing it as a pagan attack on Christianity, the writer having concealed his identity for personal safety.

It has been suggested that "Trebellius Pollio" and "Flavius Vopiscus Syracusius" were invented, with one theory arguing that their origins are based on passages in Cicero's letters and speeches in the 1st century BC.

19.12.14), Ammianus describes the Christian emperor Constantius II's attempts to prosecute cases of magic under treason laws, in particular the death penalty applied to those men who were condemned simply for wearing an amulet to ward off diseases: "si qui remedia quartanae vel doloris alterius collo gestaret" ("For if anyone wore on his neck an amulet against the quartan ague or any other complaint").

[72] Other theories include André Chastagnol's minimalist opinion that the author was a pagan who supported the Senate and the Roman aristocracy and scorned the lower classes and the barbarian races,[73] while François Paschoud proposed that the last books of the History are in fact a type of alternative historical narrative, with events and the personalities of recent 4th century emperors woven into the fabric of a series of 3rd century emperors.

[12][74] Older historians, such as Edward Gibbon, not fully aware of its problems with respect to the fictitious elements contained within it, generally treated the information preserved within it as authentic.

[75] So when Gibbon states "The repeated intelligence of invasions, defeats, and rebellions, he received with a careless smile; and singling out, with affected contempt, some particular production of the lost province, he carelessly asked, whether Rome must be ruined, unless it was supplied with linen from Egypt, and arras cloth from Gaul",[76] he is reworking the passage in The Two Gallieni: I am ashamed to relate what Gallienus used often to say at this time, when such things were happening, as though jesting amid the ills of mankind.

The reign of his immediate successor was short and busy; and the historians who wrote before the elevation of the family of Constantine could not have the most remote interest to misrepresent the character of Gallienus.

"[78] Modern scholars now believe that Gallienus' reputation was posthumously maligned, that he was one of the main architects of the later Roman imperial structure, and that his reforms were built upon by succeeding emperors.

[84] A peculiarity of the work is its inclusion of a large number of purportedly authentic documents such as extracts from Senate proceedings and letters written by imperial personages.

[90][91][92] The History cites dozens of otherwise unrecorded historians, biographers, letter-writers, knowledgeable friends of the writers, and so on, most of whom must be regarded as expressions of the author's creative imagination.

[52] The various biographies are ascribed to different invented 'authors', and continue with the dedicatory epistles to Diocletian and Constantine, the quotation of fabricated documents, the citation of non-historical authorities, the invention of persons, extending even to the subjects of some of the minor biographies, presentation of contradictory information to confuse an issue while making a show of objectivity, deliberately false statements, and the inclusion of material which can be shown to relate to events or personages of the late 4th century rather than the period supposedly being written about.

[135] As a result, his translation of the History for Penguin Books covers only the first half, and was published as Lives of the Later Caesars, Birley himself supplying biographies of Nerva and Trajan (these are not part of the original texts, which begin with Hadrian).

His view (part of a tradition that goes back to J. J. Müller, who advanced Marius' claims as early as 1870, and supported by modern scholars such as André Chastagnol) was vigorously contested by Ronald Syme, who theorized that virtually all the identifiable citations from Marius Maximus are essentially frivolous interpolations into the main narrative source, which he postulated was a different Latin author whom he styled 'Ignotus ("the unknown one"), the good biographer'.

[139] Finally, that the composer of the Historia Augusta wrote the lives of the emperors through to the Life of Caracalla, including Lucius Verus, using Ignotus as his main source, and supplementing with Marius Maximus on occasion.

[142] A similar theory to Syme's has been put forward by François Paschoud, who claimed that Maximus was probably a satirical poet, in the same vein as Juvenal and not an imperial biographer at all.

For much of that time the assessment has been critical, as demonstrated by the analysis put forward by David Magie: The literary, as well as the historical, value of the Historia Augusta has suffered greatly as a result of the method of its composition.

The over-emphasis of personal details and the introduction of anecdotal material destroy the proportion of many sections, and the insertion of forged documents interrupts the course of the narrative, without adding anything of historical value or even of general interest.

Finally, the later addition of lengthy passages and brief notes, frequently in paragraphs with the general content of which they have no connexion, has put the crowning touch to the awkwardness and incoherence of the whole, with the result that the oft-repeated charge seems almost justified, that these biographies are little more than literary monstrosities.[145]M.

L. W. Laistner was of the opinion that "even if the Historia Augusta was propaganda disguised as biography, it is still a wretched piece of literature",[146] while Ronald Syme noted that with respect to the author's Latin prose: He was not an elegant exponent.