From a Washington Post review by Oliver Traldi headlined “The biography of a brilliant philosopher reads like mystery story”:

The stunningly original British philosopher Derek Parfit, who died in 2017, was known for work that forms the core of the modern metaphysical study of personal identity. With the help of some sci-fi thought experiments, he famously argued that there is sometimes no answer to the question of whether a person at one point in time is the same as a person at another time.