Tacitus opens the Annals with a succinct sketch of the constitutional history of Rome from the kings to Augustus (1.1.1). The common interpretation holds that Tacitus adopts a cyclical view of this history which identifies the supremacy of Augustus with kingship, and chooses his vocabulary of power primarily with stylistic variation in mind. The terms employed, princeps and imperium, are also held to announce a major interpretative preoccupation of the Annals, the gap between the 'appearance' and the 'reality' of power under the principate. This essay will demonstrate that these interpretations of the structure and language of the preface are misleading. Tacitus offers a sequential view of Roman constitutional history that casts Augustus as a pivot between the tradition stretching back to the foundation of the city and a new phase which he identifies in its own terms, not as a reversion to kingship. The introduction of the motif of 'appearance v. reality' comes not with the language of princeps and imperium, but at 1.2.1. An appendix analyses the use of the term principatus in Velleius Paterculus and Tacitus.