This volume presents eighty-nine letters exchanged between John Stuart Mill and Auguste Comte between 1841 and 1847. They address important issues of the mid-nineteenth century in philosophy, science, economics, and politics. Cumulatively, these letters provide a humanistic view of Western Europe and its social problems. They add valuable perspective to what we know about the work of Mill and Comte, in a critical period of English and French thought. The correspondence begins with an admiring letter from Mill who considers himself a positivist at the tune and writes to Comte as to an elder colleague. A close friendship developed, in the course of which they discussed matters of common concern. Their understanding extends to personal experiences, including their respective mental crises at an early age. The opinions expressed about their contemporaries are significant and include comments on Thomas Carlyle, John and Sarah Austin, and Alexander Bain, on philosophers and major authors in France, Germany, and Italy. Mill and Comte eventually encountered issues on which they could not come to consensus, especially the equality of women. While Mill was an ardent defender of women's rights, Comte supported the traditional hierarchy that endowed men with social and political superiority. According to Jerome H. Buckley, Gurner Professor of English Literature Emeritus at Harvard University, "The correspondence of Mill and Comte, now available for the first time in English translation, is a remarkable intellectual exchange, a dialogue of real significance in the history of ideas." This volume will be of great interest to philosophers, historians, economists, women's studies scholars, and political scientists.