What We Can Know is the 18th novel by author Ian McEwan, published on 18 September 2025 by Jonathan Cape. The novel is set almost a century in the future, in 2119, in a UK partially submerged by rising seas, and is centred on Tom Metcalfe, an academic at the fictional University of the South Downs, who is investigating a lost poem, read aloud at a party in 2014.