The Victorian period in Britain was an “age of reform.” It is therefore not surprising that two of the era's most eminent intellects described themselves as reformers. Both William Whewell and John Stuart Mill believed that by reforming philosophy—including the philosophy of science—they could affect social and political change. But their divergent visions of this societal transformation led to a sustained and spirited controversy that covered morality, politics, science, and economics. Situating their debate within the larger context of Victorian society and its concerns, this book shows how two very different men captured the intellectual spirit of the day and engaged the attention of other scientists and philosophers, including the young Charles Darwin. Mill—philosopher, political economist, and Parliamentarian—remains a canonical author of Anglo-American philosophy, while Whewell—Anglican cleric, scientist, and educator—is now often overlooked, though in his day he was renowned as an authority on science. Placing their teachings in their proper intellectual, cultural, and argumentative spheres, the book revises the standard views of these two important Victorian figures, showing that both men's concerns remain relevant today. A philosophically and historically sensitive account of the engagement of the major protagonists of Victorian British philosophy, this is the first book-length examination of the dispute between Mill and Whewell in its entirety.