Derek Parfit
Derek Parfit (11 December 1942 – 1 January 2017) was a British philosopher whose work focused on personal identity, practical ethics, and rationality.[1][2] A Fellow of All Souls College, Oxford, for much of his career, Parfit also held visiting positions at Harvard University and other institutions.[3][1] In his seminal book Reasons and Persons (1984), Parfit argued that personal identity is not what matters in survival or ethics, but rather "Relation R"—psychological continuity and connectedness with preserved causes—challenging egoistic intuitions and advancing reductionist views of the self.[3][4] His later work On What Matters (2011, with volumes extending to 2017) sought to converge Kantian, contractualist, and consequentialist ethics into a unified non-naturalist framework, emphasizing reasons-based morality over subjective desires.[3][4] Parfit's explorations of population ethics, including the Repugnant Conclusion, highlighted tensions in utilitarian aggregation and our duties to future generations, influencing debates on impartial altruism and longtermism.[3][4] These ideas contributed to the philosophical foundations of effective altruism, a movement Parfit supported in his later years through discussions on optimizing altruistic impact across time and space.[5][6] Widely regarded as one of the most important moral philosophers of the late twentieth and early twenty-first centuries, his rigorous, first-person analytical style reshaped ethical theory by prioritizing logical consistency over conventional boundaries.[4][3]