This volume begins to explore the life and works of Auguste Comte during his so-called second career, the controversial period that began in 1842 and lasted until his death. This volume covers the years from 1842 to 1852, when Comte transformed his positive philosophy into a political and religious movement. It represents the first in-depth study of that movement. Focusing on key books, such as the Discours sur l'ensemble du positivisme, Mary Pickering connects Comte's intellectual development to the tumultuous historical context and to episodes in his personal life, especially his famous relationship with Clotilde de Vaux. The book examines for the first time why workers, doctors, women, and famous writers, such as John Stuart Mill, George Henry Lewes, and Emile Littré, were drawn to his thought.