This work investigates the intellectual evolution and personal life of Derek Parfit, one of the most influential moral philosophers of the twentieth century. Jeff McMahan, a philosopher and close associate of Parfit, utilizes personal correspondence, unpublished manuscripts, and extensive interviews to reconstruct Parfit's rigorous approach to identity, rationality, and ethics. The text argues that Parfit's radical conclusions regarding personal identity were inextricably linked to his unique, obsessive methodology and his commitment to objective moral truth.

Experts recognize this volume as the definitive biographical account of Parfit's life and intellectual trajectory. Readers frequently note the academic density of the prose, which assumes a foundational understanding of contemporary moral philosophy.