The great Greco-Roman historians regularly testified that their content was derived from 1st hand experience (their own or that of witnesses who they interrogated), or was at least grounded in witness-testimony (2nd hand, maybe 3rd).
• Josephus, Luke, Tacitus, Nepos, Polybius, Theopompous, Xenophon, Herodotus etc. boast “I saw events xyz 1st hand”
• Philostratus (170-250 AD): “[He] honoured me also with one interview, then with a second and a third… And in fact all that I have recorded above about those sophists I stated on the authority of Damianus, who was well acquainted with the careers of both.” [Lives of the Sophists 2.23.606]
• Flavius Josephus (37-100 AD): …”[Regarding my prior work:] …when all my materials were prepared for that work, … I composed the history of those transactions; and I was so well assured of the truth of what I related, that I first of all appealed to those that had the supreme command in that war, Vespasian and Titus, as witnesses for me, for to them I presented those books first of all, and after them to many of the Romans who had been in the war. … Now all these men bore their testimony to me, that I had the strictest regard to truth…” [Against Apion 1.50-55]
• Dionysius of Halicarnassus (60 BC-7 AD+): “Hitherto I was ignorant of all this; but now, having learned of it through information given me and having many credible witnesses and having also examined the slave, I have recourse to…” [Roman Antiquities 11.29.3]
• Polybius (200-118 BC): “so that I have been present at some of the events and have the testimony of eyewitnesses for others. [otherwise] I should be safe neither in my estimates nor in my assertions.” [The Histories 4.2.1] (E.g. He testifies to using Gaus Laelius, Perseus’s friends, various Carthaginians, and the African prince Gulusa as witnesses).1
• Herodotus (484–425 BC): “…I know this, because I was told at Dodona…” [The Histories 2.52] (See more here on Herodotus’s travels and witness-interrogations)
Greco-Roman historians jumped quickest to record events they saw 1st hand. Compared to modern history, writings of ancient historians are disproportionately about things historians were themselves involved in.
• E.g. see these historians boast of being 1st hand testimony.
• E.g. They used their memoirs.1
• Flavius Josephus (37-100 AD) says “My history is a 1st hand”2
• Luke (AD 70) says he participated in what he narrates.
• Luke wrote most elaborately on the sea voyage he attended.
• Tacitus (56-20 AD) says he was a witness3
• Cornelius Nepos (110–25 BC) says he witnessed relevant events.4
• Polybius (200-118 BC) did.5
• Theopompous (380-315 BC) did.6
• Xenophon (430-354 BC) wrote a lot of 1st hand witnessed history.7
• Herodotus (484–425 BC) boasted of it.8
Historians in the 1st-2nd century would sometimes tip readers off to their witnesses by how they conspicuosly included the person in the account, especially at a key moment where a witness would be needed.
• Examples abound (from Plutarch, Nepos, Josephus).
Greco-Roman historiographers tended to successfully ground their material in witness testimony or approval.
• Historians strove for a 1st-hand-as-possible history.
• Histories self-identify as witness-testimony.
• Historians oft felt 2nd-3rd hand etc. unacceptable.
• Greco-Roman histories self-claim to be true.
• More forthcoming.