After the death of Tacitus the Muse of history maintained virtual silence in the Latin west for two and a half centuries. This is partly to be explained by the role of history in Roman culture. Traditionally, the writing of history— the history of one's own times or of the immediately preceding age—had been an occupation for retired or failed statesmen, an aspect of their otium which corresponded to their political negotium. This meant that it was essentially an activity of senators. From Cato the Censor through Calpurnius Piso, Caesar, Sallust, Asinius Pollio, Cluvius Rufus to Tacitus the succession of senatorial historians stretches across the centuries. But by Tacitus' time there was no longer an independent political role for senators to play. They needed neither to proclaim their successes nor to justify their failures. The making of decisions had passed into other hands than theirs. They could only look back nostalgically and recount the successive stages by which they had lost their libertas (in the special sense which the word bore in senatorial thinking). After Tacitus' time it was too late to do even that. The memory of libertas had perished. At the same time the composition of the senatorial class itself had changed. From being a small, close-knit, relatively exclusive group of central Italian landowning families, traditionally concentrating in their hands the exercise of the power of the Roman res publica, in spite of, or sometimes thanks to, the occasional maverick who appealed over the heads of his colleagues to the people of Rome, it had become a wide-open group of upper-class families from Italy and the western provinces, with little of the old solidarity or sense of destiny.