This book explores the theological, intellectual, and political struggles surrounding the Jansenist movement in 17th-century Catholicism. Centered on the controversial ideas of Cornelius Jansen, which emphasized the radical sovereignty of divine grace and the total depravity of human nature, the book traces the rise of Jansenism as it challenges the more lenient doctrines of the Jesuits, particularly the role of human free will in salvation. Through the lens of key figures such as Blaise Pascal, Antoine Arnauld, and the influential Port-Royal Abbey, the narrative examines the theological debates that set the Jansenists against both the Catholic monarchy and the papacy. The work delves deeply into the political ramifications of Jansenism's challenge to the Church, including the role of King Louis XIV and the Jesuit order in suppressing the movement. The systematic attempts to silence the Jansenists, from papal condemnations to the destruction of Port-Royal in 1710, serve as a backdrop for an exploration of broader themes, including the tension between ecclesiastical authority and intellectual dissent, as well as the evolving relationship between religion and politics in early modern Europe. In addition to offering a detailed historical account of the Jansenist movement's rise and fall, the book reflects on its lasting intellectual legacy and highlights how the theological questions raised by the Jansenists—about grace, predestination, and free will—continued to resonate through later Reformation thought, Enlightenment critiques of institutionalized religion, and Catholic moral teachings. Through this examination, the book not only sheds light on an important episode in Catholic history but also explores enduring theological issues that continue to shape Christian discourse today.