Donne isn't merely saying that letters carry our thoughts across distance—he's making a bolder claim about intimacy itself, suggesting that written correspondence creates a kind of spiritual fusion that transcends the merely communicative. There's something almost alchemical in his verb "mingle": souls don't simply exchange information; they blend and interpenetrate through the act of writing and reading. When you write a genuine letter, you leave traces of your inner life on the page, and the recipient absorbs not just your words but something of your presence—which is precisely why a handwritten note from someone you love still moves us in ways an email rarely does, decades later.