Since the publication of the first edition of Richard Popkin’s classic The History of Scepticism in 1960, skepticism has been increasingly recognized as a major force in the development of early modern philosophy. This book provides a review of current scholarship and significant updated research on some of the main thinkers and issues related to the reappraisal of ancient skepticism in the modern age. Special attention is given to the nature, importance, and relation to religion of Montaigne’s and Hume’s skepticisms; to the various skeptical and non-skeptical sources of Cartesian doubt; to the skeptical and anti-skeptical impact of Cartesianism in the seventeenth and eighteenth centuries; and to philosophers who dealt with skeptical issues in the development of their own various intellectual interests.