Further meditations on Sense and Sensibility made me think about how letters drive the story. A letter from Sir John spirits the Dashwoods from Norland to Barton; a letter from Eliza Williams impels Colonel Brandon from Devonshire to London, and precipitates Willoughby's ultimate downfall; letters between Marianne and Willoughby are a revelation to Elinor as well as a catastrophic eruption, in the relationship between M and W, and in that between W and his fiancee. Mirroring Brandon's unhappy receipt of Eliza's letter while in company, Willoughby receives Marianne's letter while he is breakfasting with his new in-laws, and the truth of his perfidy is outed again, this time to his own shame, instead of to his victim's. Lucy's letters, more than her conversation, reveal how “ignorant, illiterate and artful” she is, and how unworthy to be Edward's wife; Elinor is struggling with the composition of her letter to Edward - a letter that must be extremely painful to both - when he walks in on her and begins their most exquisitely awkward and yet most tender and revelatory exchange.
Probably in the other novels, too, letters are important, but in this novel about painful suppression and unspoken feelings, they are all the more necessary as touchstones of emotion and instruments of action.