Allyn Waller, Stanford University
Omnium consensu, capax imperii, nisi imperasset. This dictum from Tacitus’ obituary of Galba (Histories 1.49) has mostly attracted attention for its conditional statement (e.g. Heubner, Damon). In addition, the phrase capax imperii was taken up by Sir Ronald Syme and others to address the concept of “could-have-been” emperors (Syme 1955, 1958, and 1979, Benario). Omnium consensu, on the other hand, has received scant attention. However, upon closer inspection, Tacitus appears (1) to emphasize consensus as a core element of Galba’s reign, and (2) to borrow this phrase from a common coin slogan of Vitellius, one of Galba’s successors in 69 CE.
Consensus is rare in Tacitus’ works, with only 6 uses outside the Histories, but 20 within it. This concentration in usage is mirrored by a concentration in focus. All 12 usages in Book 1 relate to Galba’s claims to power. Galba in his adoption of Piso attributes the source of his imperial power to consensus (nunc me deorum hominumque consensu ad imperium vocatum, 1.15). In Piso’s response, he echoes Galba’s phrasing, but strengthens consensus as the nominative subject (Galbam consensus generis humani, me Galba consentientibus vobis Caesarem dixit, 1.30). When Galba’s reign falls apart, he is consensu errantium victus (1.35). Consensus drives Galba’s rise and fall.
RIC lists 14 coin types of Vitellius, including gold, silver, and bronze, with the legend “CONSENSUS EXERCITUUM”. Could these be Tacitus’ inspiration? Tacitus notes that nomen Germanici Vitellio statim additum: Caesarem se appellari etiam victor prohibuit (Hist. 1.62). Suetonius and Plutarch agree on this refusal as well (Plut. Galb. 22.7 and Suet. Vit. 8.2). Of the 177 Vitellian coin types listed in RIC I2, almost all have GERMANICUS, but not a single coin has CAESAR. This is true even as Vitellius takes on more and more imperial titles. (e.g. RIC I2 Vitellius 115 “A[ULUS] VITELLIUS GERMANICUS IMP[ERATOR] AUG[USTUS] P[ONTIFEX] M[AXIMUS] TR[IBUNICIAE] P[OTESTAS]”) Vitellius is indeed the only emperor not to be called Caesar on coinage. As Bocciarelli argues, this may be an attempt to establish Germanicus as a cognomen of a new dynasty in opposition to the Julio-Claudian Caesar. The coinage and the historians all agree on this use of Germanicus and avoidance of Caesar, seemingly reflecting a real piece of Vitellius’ imperial propaganda. This indicates that Tacitus had access to “CONSENSUS EXERCITUUM” to rework as a leitmotif for Galba. But why would he?
Of the emperors up to Trajan, Galba had the least consensus; he inherited from Nero multiple ongoing rebellions, including that of Vitellius. He only added to these with Otho’s coup. Tacitus transfers the irony of Vitellius’ claims to be the consensus exercituum (despite only regional support) to Galba (who ultimately loses even that). Tacitus also inflates the claim to omnium consensus (and synonyms: see 1.15, 1.30). This magnifies the irony. As the climax of the leitmotif, it is a fitting opening for capax imperii, nisi imperasset.