When a poet addresses a living person--whether friend or enemy, lover or sister--we recognize the expression of intimacy. But what impels poets to leap across time and space to speak to invisible listeners, seeking an ideal intimacy--George Herbert with God, Walt Whitman with a reader in the future, John Ashbery with the Renaissance painter Francesco Parmigianino? In Invisible Listeners, Helen Vendler argues that such poets must invent the...