Reading Correspondence for Tone as Well as Content
Launch library · evergreen read

A letter carries information in two layers at once: what it explicitly says, and how it goes about saying it, and formality, warmth, brevity or evasiveness can each reveal something about the relationship and circumstances behind the words that a purely literal reading would miss entirely on its own.
Reading for tone requires comparing a given letter against others from the same correspondent, since a formal register might simply be that particular writer's habitual style rather than a meaningful shift worth noting carefully in a single piece of writing considered entirely in isolation, without the benefit of anything else written by the same hand.
Used carefully, tone can support a documentary claim without ever becoming the claim itself, since it adds texture and context to a fact already established elsewhere, rather than serving as standalone proof of anything specific entirely on its own, however revealing that tone might genuinely seem to a careful reader.