The literary world – well, the bit of it on X/Twitter – had a small conniption last week. One American poet claimed that another’s unrhymed, unmetered sonnets were “not poetry”, merely “prose”. According to the site, their spat drew the attention of a quarter of a million people, far more than will ever buy either writer’s books. Why does the “Is this a poem?” debate still get people so worked up? Everyone agrees Anne Carson is a poet – to some, the greatest living poet – and her poetry is often in prose. In 40 years of publications, she has consistently answered “yes, both” to either/or questions: fiction or nonfiction, prose or verse, translation or original writing. Her books include verse novels, a poem-essay on Proust, a comic-book version of a Greek tragedy, and a bundle of pamphlets designed to fall out of their box onto the floor in a random order.…