Different kinds of historical evidence permit different kinds of argument. Rivet totals illustrate questions about countable physical features, although checking them becomes difficult when the ship no longer exists. An autobiography's explanation of why its author acted is more open to interpretation. People sometimes misunderstand their own motives, so a first-person account does not by itself settle the reasoning behind a decision.
Notable Point · 25:20-26:58
Why autobiographies do not settle historical motives
A person's account of their own motives needs interpretation, just as historians must distinguish physical evidence from conclusions drawn about it.