Letters have the power to grant us a larger life. They reveal motivation and deepen understanding. They are evidential. They change lives, and they rewire history. The world once used to run upon their transmission — the lubricant of human interaction and the freefall of ideas, the silent conduit of the worthy and the incidental, the time we were coming for dinner, the account of our marvelous day, the weightiest joys and sorrows of love.