From the first, it was realised that The Decline and Fall was in some respect ‘Tacitean’. Mme Necker wrote to her old lover in September 1776 that

There is something both amusing and touching in the would-be bluestocking's determination to show Gibbon that she can still converse with him on literary topics as an equal, as she had done in the ‘societé du printemps’ at Lausanne. Certainly, the connexion with Tacitus seems well calculated to flatter Gibbon, and modern criticism has singled out his consanguinity with the author of the Annales and Historiae as a profound truth. However, we saw in the portrait of Augustus that Gibbon is no bondman of the senatorial historian. Although he has a great respect for Tacitus, the substance of what he has to say in The Decline and Fall is different from while being thoroughly informed by the Tacitean perspective on Roman history.

This careful separation of The Decline and Fall from Tacitus, the gravitational pull of whose work Gibbon acknowledges but to which he does not succumb, is visible once more in Chapter IX, where he assesses the magnitude of the barbarian threat to the empire.