I. In her smart introduction to The Penguin Book of the Sonnet, Phillis Levin describes the famous fourteen-line form as “a chamber of sudden change.” ¹ The fulcrum of that change is the volta, the sonnet’s leap or turn—typically, but not always, between the octet and sestet. But wherever it occurs, as Levin says, the turn is the point at which the reader “reconfigures the experience of all the lines that both precede and follow it.” ² Levin’s idea of “sudden change” applies equally, I think, to a strong turn in any poem. So does her idea of “chamber.” There’s a way in which the turn in a poem itself is a chamber of sudden change, a place with height and depth and width,…