When we write history, we cite our sources. We do this so that those reading the history will know from where we get our information. If we use footnotes, we can explain how we get to that piece of evidence or that conclusion.
Our main sources (Tacitus, Suetonius, Cassius Dio) for the reign of Tiberius and, indeed, for all the Julio-Claudian emperors, lived and wrote much later than the events they discussed. So how do they know what happened?
The footnote did not exist. Historians only very rarely talked about their sources and normally only when they disagreed violently or the sources that they were reading had differing accounts. So what do we imagine that they had at their disposal?
Historians working in Rome primarily (Tacitus and Suetonius) would have had access to some archival material.
Acta Senatus: These were the records of senatorial actions. They were probably extended summaries. They likely included the proposals put before the senate; the names and arguments of the chief speakers; the decisions of the senate.
Senatus Consulta: The decrees of the senate. These were normally quite fulsome. These were not laws, though they were more than advisory under the empire. But because they were not laws, they explained why things were done. They were political documents.
Laws: Most elite Romans would have had familiarity with laws. Laws were not primary instruments of government in the way in which modern states often act. The passing of a law was normally either to modify existing practice or to deal with a serious issue.
Commentarii of the magistrates: Magistrates would keep records of their acts in day books. They did this so that those acts which had legal and administrative force, and most magistrates acted as judges, would be recorded and could be consulted. We don’t know how complete they were, but it seems possible that the scribes who maintained the commentarii would keep quite good notes. Magistrates would report their deeds to the senate, but we don’t know how full those accounts would be.
Letters/documents/decrees: A considerable amount of Roman administrative practice was on paper. As we can see from Pliny’s Letters 10, a governor might keep up a regular correspondence with the emperor, asking advice, checking procedures, and telling him what was going on. Pliny might have been an especially bust correspondent. But when Piso was tried for his actions in relation to the death of Germanicus, letters and memoranda were produced from which the senate could reconstruct the acts of Piso and Germanicus and relations between the two. Provincial communities would also consult emperor and and senate, and those consultations would generate paperwork.
We would then expect there to have been enormous archives of material relating to the histories of the various emperors. But did the historians consult those archives?
It looks as though Tacitus and Suetonius did. The archives seem to have been accessible and so people could check on particular issues. Suetonius had access to imperial letters, for instance. It seems likely that Tacitus took his basic narrative from the Acta Senatus. That would enable him to date particular events and gave him his narrative form.
But how systematic was their engagement?
We can only judge off impressions and the impression is that it is was literary sources that influenced their judgements more than documentary material.
Speeches: The Romans loved a good speech. They studied rhetoric. Tacitus wrote a dialogue about rhetoric in which his characters related oratorical practice to the politics of the day. Speeches were necessarily ephemeral, but the Romans took to publishing them if they thought either that they were artistically good or that they were politically important.
We don’t have many surviving. Pliny’s speech in thank of Trajan is one example. But we would expect there to have been many more circulating.
The speech of an emperor, for instance, might well get published. What better way was there to honour the importance of the imperial words? If the occasion was important enough, they might even get inscribed, as happened to Tiberius’ speech on the death of Germanicus.
One presumes that they were around to inform historians.
Histories, Accounts and Memoirs
The Romans used history as political commentary. They were not shy of contemporary history. Tacitus complains of the quality of the histories that he had to read when writing the Annales. People were writing to praise the emperor while the emperor lived. Once the emperor had died, they might write to blame. They wrote to honour the dead in imperial persecutions. They wrote to excuse themselves or revenge themselves. The fact that Tacitus claimed to write sine ira et studia (without anger or partiality) in Annales 1.1 is evidence in itself that others were not so careful.
There was no shortage of material and some of it was probably eye-witness. But it did not always agree. We also cannot know how careful our sources’ sources would have been. Might they have invented? Might they have used a malicious imagination and passed it off as fact?
It is clear that the historians were aware of those problems, in particular when dealing with things like Nero’s relationship with his mother or Claudius’ relationship with his freedmen or the influence of Livia, material which by its very nature was likely covert. But what could they do about it?
They sorted through the material. They don’t just report all the stories. But the basis on which they split the truth from the fictional is not obvious. They tried to generate an internally coherent narrative which made sense.
And that’s what we get. It must have made sense to them. Consequently, it is near impossible from the texts themselves to distinguish fact from fiction. Indeed, if we think that we can detect something that is clearly fictional, we ought to worry: why is it there? why was it not edited out? We might question their interpretations, but the factual content was unlikely to be very wrong.
When we do our assessments and write our histories using this material, we should be critical, but sensibly so. We might suspect invention, but need to consider why we can see it. We need to respect the sources, but not have our views determined by them. We work with them, not against them.