This book explores the rise, influence, and eventual decline of Jansenism, a theological movement rooted in the teachings of St. Augustine, which had a profound impact on the religious, intellectual, and political landscapes of 17th-century France. At the heart of Jansenism is a radical critique of Jesuit theology, particularly their views on grace, free will, and salvation. The Jansenists, led by figures such as Cornelius Jansen, Blaise Pascal, and Antoine Arnauld, emphasized the total depravity of human nature, the necessity of divine grace, and the rejection of human cooperation in the process of salvation. The book traces Jansenism's intellectual and theological journey, from its early roots in Port-Royal Abbey to its eventual suppression by the papacy and the French monarchy, highlighting the political and ecclesiastical battles surrounding its teachings. Through a detailed exploration of primary sources, including key writings from Jansenist theologians and their Jesuit opponents, the book examines the lasting influence of Jansenism on both Catholic and Protestant thought, as well as its impact on the development of moral philosophy and the modern theological landscape.