Denominational identity, though poorly understood in theological terms, was socially decisive to postwar Americans. Lowell’s lifelong preoccupation with religion took the form of an ostentatious Catholicism in the 1940s, influenced his conscientious objection to World War II, and helps explain his poems about Jonathan Edwards. Paul Mariani discussed Lowell as a “Lost Puritan,” while Kay Jamison investigated the proximity of madness and faith as “states of possession,” and Elisa New sees a “visionary” impulse in the poet. Milton and Hopkins stimulated Lowell’s poetry as much as questions of ethics troubled it. Lowell’s religious temperament remained permanently alert, calling into questions fossilized distinctions between early and late Lowell. Its recognition and contextualization provides interpretive access to his monologues and family portraits from Mills of the Kavanaughs to Life Studies, resurfacing wistfully in Day by Day.