Quick questions on The fall of the Roman Republic 78-42 BC survey and sources: HSC Ancient History

The senator and orator Cicero (106 to 43 BC) left an enormous body of contemporary writing: private letters (the collections Ad Atticum, Ad Familiares, Ad Quintum Fratrem), public speeches (the Catilinarians of 63 BC, the Philippics attacking Antony in 44 to 43 BC), and rhetorical and philosophical works. The letters in particular are unmatched: unguarded, real-time reactions from inside the elite, published only after his death. But Cicero was a partisan actor whose attitudes shifted with events, so his testimony reveals feeling and allegiance more than settled fact.

Caesar's own Commentarii, the Bellum Gallicum (on the conquest of Gaul, 58 to 52 BC) and the Bellum Civile (on the war with Pompey, 49 to 48 BC), are a participant's first-person narratives, written in a plain third-person style. They are invaluable but deliberately self-serving: motives, casualty figures and the justice of his cause are all shaped to defend his political position.

The historian Sallust (c. 86 to 35 BC), a former Caesarian, wrote the monographs Bellum Catilinae and Bellum Iugurthinum and a now-fragmentary Histories. He is a near-contemporary voice, but he writes to a thesis: that Roman virtue decayed once the fear of Carthage was removed after 146 BC, driving the Republic toward ruin.