Théologien du Grand Siècle, minor de la République des Lettres, Isaac Papin (1657-1709) est né calviniste. Il appartient à l'École théologique dite de Saumur : fils spirituel du théologien novateur Claude Pajon (son oncle), il adopte les théories de ce dernier sur la grâce et, lecteur de Spinoza dès 1681, développe une conception originale de la tolérance à une période d’effervescence sur cette question dans la pensée protestante. Au moment de la révocation de l'édit de Nantes, Papin rejoint le Refuge : il est alors proche de citoyens des Lettres comme Jacques Lenfant, Jean Le Clerc et Pierre Bayle. Il s’installe d'abord en Angleterre où il est ordonné prêtre de l'Église anglicane puis se rend aux Provinces-Unies, puis dans le Saint-Empire où il tente de s'installer comme pasteur d'une Église wallonne. Son identité de novateur déclenche l'opposition de l'orthodoxe Pierre Jurieu (déjà ennemi de Pajon) qui l'empêche d'atteindre son but. Il décide alors de se convertir et revient en France en 1690, où il passe au catholicisme grâce à Bossuet. Jusqu’alors nomade huguenot de la République des Lettres, Papin se mue en catholique sédentaire dans sa ville natale, Blois : il devient l'un des acteurs de la controverse antiprotestante et se rapproche du jansénisme grâce à l’un de ses amis,également pasteur calviniste converti. En associant histoire sociale des réseaux théologiques et religieux et histoire des idées et des controverses, cette biographie intellectuelle retrace la trajectoire théologique particulière d’un converti du Grand Siècle passé de l’humanisme réformé de Saumur à un jansénisme entre Nicole et Quesnel. / Theologian of the Grand Siècle, minor of the Republic of Letters, Isaac Papin (1657-1709) was born Calvinist. He belongs to the so-called theological school “École de Saumur” : spiritual son of pioneering theologian Claude Pajon (his uncle), he adopts his theories on grace and, as Spinoza reader from 1680, he develops an original design of tolerance during a boom period on this issue in Protestant thought. At the time of the Revocation of the Edict of Nantes, Papin joins the Refuge : he is then close to Letters’ citizens such as Jacques Lenfant, Jean Le Clercand Pierre Bayle. He first moves to England where he is ordained priest of the Anglican Church. Then he goes to the United Provinces and to the Holy Empire, where he tries to settle as a pastor of a Walloon Church. His innovative identity triggers opposition from the Orthodox Pierre Jurieu (Pajon’s former enemy) that prevents him from reaching his goal. He decides to convert and returns to France in 1690, where he becomes a Catholic under the authority of Bossuet. Until then nomadic Huguenot of the Republic of Letters, Papin turns into a sedentary Catholic in his hometown, Blois.He becomes one of the actors of the anti-Protestant controversy and approaches the Jansenism thanks to a friend who is also a converted Calvinist pastor. By combining social history of theological and religious networks and history of ideas and controversies, this intellectual biography traces the particular path of a theologian converted of the Grand Siècle, from reformed humanism of Saumur to Jansenism, between Nicole and Quesnel.

John Cameron highly influenced the development of theology at the Huguenot Academy of Saumur and left an impact on French Reformed thought that continued to the end of the Seventeenth Century. Cameron had modified orthodox Calvinism by softening some of its harsher features in order to answer its opponents more effectively. Claude Pajon was convinced that certain flaws had emerged in the way other disciples of Cameron were interpreting his theology which threatened to undermine Cameron's carefully balanced system. Cameron had introduced the concept that the will always follows the understanding and that man is converted according to his nature through persuasion and reasons without any coercion. Man was understood as possessing natural ability to choose the good; however because of his own voluntary choice, he remains in the grip of a moral inability. He also taught the controversial concept of "hypothetical universalism" or that God wills the conversion of all men and provides the Word for their redemption which is an adequate remedy for man's sinful condition. In the end, however, only those granted a particular grace are actually of the elect and converted. Pajon vigorously opposed those who argued that there is a need for an immediate act of grace distinct from the action of the Word before man's mind could be illuminated. To argue that grace is universal and that the Word is an adequate remedy for sin and still to insist on an immediate grace of this nature was considered by Pajon to rob the concept of universalism of any validity, and to undermine the entire Cameronian apologetic. Pajon's solution was to propose a method of conversion known as mediate grace or congruism. The Spirit brings about conversion entirely by the secondary means of the Word and its attending circumstances and causes all these influences to converge in such a way and at such a time that the subject is inevitably but voluntarily persuaded and converted. It is essential to the very nature of man to be able to receive the Word of truth which brings deliverance to the soul without immediate grace. Furthermore, man's sin is of a moral nature; nothing physical is involved in it in any way. Therefore, the logical prescription should be a moral remedy for a moral malady. Pajon understood that his concept of grace represented Cameron's own position and was the most coherent interpretation of Cameronianism.