Unlike Bishop, Lowell was one of the original Confessional Poets. Along with Sylvia Plath, Anne Sexton, and others, Lowell drew from his own life for material to write poems in the new, looser art form he was helping to create. Lowell’s Life Studies showed two aspects of confessional poetry: the commitment to craftsmanship and the willingness to talk about real-life events in shocking, groundbreaking ways. This poetry pushed against genre-based and societal boundaries of what was or wasn’t acceptable to talk about. In the early days of this movement, the 1950s and 1960s, examples included Plath’s unfiltered accounts of her suicidal thoughts or Sexton’s thoughts on menstruation at age 40.

Bishop, meanwhile, hated confessional poetry. She didn’t much like that shift in Lowell’s later poems, and she definitely didn’t like the tell-all poems about sexual escapades written by the college students she taught. But her major problem with Lowell came when he used his wife Elizabeth Hardwick’s pain to lend narrative intensity to The Dolphin—when he wasn’t confessing just for himself but for someone else. In responding to the poems Lowell sent her, Bishop drew a distinct line: Probe your own life and past if you must, but you cannot use another person’s trauma without permission for your aesthetic gain.

Hardwick, herself a writer, had endured a tumultuous marriage with Lowell that included his many affairs and mental breakdowns. In 1970, Lowell left Hardwick for another woman, Caroline Blackwood, with whom he had a child and who he eventually married. After he left, Hardwick wrote him a series of intimate letters in which she laid out her angst and grief. Lowell turned those letters into poems for The Dolphin. In the book, he enjambs the letters to make lines and stanzas, edits the results without making clear where these changes occur, and even fictionalizes some lines—they still read like Hardwick’s letters, but they became Lowell’s work. He did not get her permission, and he told Bishop he knew it would hurt Hardwick. But he ultimately felt that the aesthetic value was worth the moral cost. As Lowell wrote Bishop later, “the letters make the book.”

Bishop was horrified. It took her weeks to write back after seeing drafts of the poems and when she did, her response was scathing. In a letter dated March 21, 1972, Bishop lets Lowell have it: “Aren’t you violating a trust? IF you were given permission—IF you hadn’t changed them ... etc. But art just isn’t worth that much. I keep remembering [Gerard Manley] Hopkins’s marvelous letter to [Robert] Bridges about the idea of a ‘gentleman’ being the highest thing ever conceived—higher than a ‘Christian’ even, certainly than a poet. It is not being ‘gentle’ to use personal, tragic, anguished letters that way—it’s cruel.”

Lowell still published the poems, and his friendship with Bishop never recovered. He never denied being cruel; he privileged his art over his kindness. In fact, he acknowledged the pain he was causing in his letter to Bishop a week later: “I did not see [Hardwick’s letters] as slander, but as sympathetic, tho [sic] necessarily awful for her to read. She is the poignance of the book, tho [sic] that hardly makes it kinder to her.” The book won Lowell his second Pulitzer Prize for Poetry. But even at the time, reviewers publicly echoed Bishop’s private concerns that Lowell had crossed an important line.