What if M. Scribonius Drusus Libo, executed for conspiracy under Tiberius in a.d. 16, was not simply the foolish young noble with imperial ambitions portrayed in Tacitus? That is one of the questions Pettinger's study addresses and in the process argues a simple but important point: the Principate did not introduce a stable political system, but was much more fragile than we have perhaps appreciated. The first chapter sets the stage for the study by summarizing Libo's case as presented in our ancient sources, then argues, based on that evidence, that Libo was a dangerous conspirator, contrary to what many scholars believe (who follow Tacitus’ lead in playing down Libo's threat). A fine, lengthy discussion follows concerning the charges under which Libo would have been indicted, and argues convincingly for an indictment under the lex de maiestate. P. then turns to Libo's treatment to argue that he was a credible and dangerous opponent to the regime. The lack of willingness on anyone's part to take up Libo's defence, Libo's being kept in protective custody (as the Catilinarians), and his damnatio memoriae after his death (and attendant thank offerings), are things one would only find in the context of a serious conspiracy.

The remainder of the study is a lengthy (and excellent) discussion that gives the background to the problem of the succession to Augustus, the instability that attended it, and the politics and personalities behind the scenes. Ch. 3 examines the political factions that worked in the interest of Augustus’ grandson, Gaius Caesar, only to turn their allegiance to Agrippa Postumus after Gaius’ death. In both instances those who worked in the interests of either were generally arrayed against those of Tiberius. But how to explain Agrippa's adoption in a.d. 4 without the same honours as his brothers Gaius and Lucius, and his swift fall from favour and relegation the next year? In ch. 4 P. argues that the difference is to be explained by Augustus’ wish to put Tiberius forward. Agrippa posed a serious political challenge that Augustus had to meet delicately; he had to be got out of the way. P. discusses the political context and background to that challenge in ch. 5. The period around a.d. 5 saw a series of events, including flood, famine, and disease throughout Rome and Italy, that led to economic as well as political and military instability, that P. argues was quite serious. Rebellion in Illyricum in a.d. 6 exacerbated the situation, and Augustus was compelled to take extraordinary measures. The public lost patience when Augustus imposed a five per cent inheritance tax to finance measures to address the crisis, which merely led to an attempt at revolution; one of those involved may have been L. Aemilius Paullus, husband of Augustus’ grand-daughter Julia. Aemilius was ultimately prosecuted, Agrippa put out of the picture, and by a.d. 7 it was clear that Augustus had thrown in his lot with Tiberius for succession and not unhappily, as the tradition would have us suppose. P. further argues that there was possibly widespread support for Agrippa who may have become a mouthpiece of opposition to Augustus (and Tiberius) in the midst of the difficulties Augustus faced at home and abroad (hence Agrippa's further relegation from Surrentum to Planasia).

Ch. 7 discusses the question of Augustus’ grand-daughter, Julia, her exile, and its relationship to Agrippa. The chapter constitutes a lengthy but interesting and ultimately relevant digression as concerns its relationship to Augustus’ attitude towards succession, but ultimately, contrary to a large body of scholarship, we should not connect it directly to Agrippa's exile. The next two chapters deal with the difficult position Tiberius found himself in during Augustus’ later years, when unrest and unpopular policies impacted public opinion concerning Tiberius who arguably acted as Augustus’ virtual co-regent. Augustus late in his reign carefully orchestrated Tiberius’ succession, as indicated by the entire empire swearing an oath of allegiance to Tiberius upon Augustus’ death. Tiberius willingly accepted power and wielded it, except in the senate, where he hedged. How to explain his hesitation? In the final chapters (10 through 12) P. argues that the potentially destabilized political situation in Rome, with Agrippa Postumus still living, the attempted usurpation by Clemens, and, above all, the rivalry of Libo, all contributed to Tiberius’ waffling. Agrippa's execution soon after Tiberius’ succession in particular presented a genuine embarrassment for Tiberius, who did not, in fact, give the order; rather it was his courtier, Sallustius Crispus, who did so. The equivocation of the government in explaining his death invited suspicion and speculation concerning the rôles of Augustus, Livia, and Tiberius. Tiberius’ government was further beset, at the first senate meeting after Augustus’ death on 17 September a.d. 14, by the news of the mutinies amongst the legions of Germany, which will have further affected Tiberius’ behaviour at that meeting, but it was not the primary factor in causing Tiberius’ hesitation. Rather, according to P., Tiberius hedged because he had misgivings about Libo, to whom Agrippa's faction will have turned, especially in the wake of Agrippa's execution. The situation was all the more acute because Tiberius had been absent from the senate between the years 6 b.c. and a.d. 13, while the faction that supported first Gaius, then Agrippa, and finally Libo will have been a formidable presence within that body, threatening his position. P. also argues for Libo's involvement in Clemens’ rebellion in a.d. 16, and that Libo and his supporters (including like-minded senators) desired nothing less than the Republic's restoration. That faction, once Libo was dead, abided well into Tiberius’ reign, and turned their support to Germanicus and then to his widow, Agrippina the Younger.

There are two difficulties in this otherwise fine study that I found bothersome. First, much of the argument is often highly conjectural (e.g., the assertion that Gaius’ followers formed a political faction against Tiberius that threw in its weight after Gaius’ death with Agrippa, then Libo), although in fairness P. is clear when making such conjectures. The second is that, while many of us would absolutely agree that Tacitus is problematic as a source, at times the argument in following other sources while questioning Tacitus seems to me rather strained. However, agree with his argument or not, P.'s study contributes significantly and commendably to our understanding of the Augustan Principate and the imperial succession.