History & CultureMental model
A fingerprint lies less often than a letter.
Sources split into two kinds. Relics arise incidentally: tools, rubbish, invoices, fingerprints. Narratives are told deliberately: chronicles, letters, monuments. Relics count as more credible because nobody composed them for you. The same questions apply to both: when, where, by whom, from what, in what form, with what evidential value.
Useful: For any source, first ask whether it was made for you or merely left over by accident.
Source: en.wikipedia.org