Hence it is largely, not entirely, true that the best of the prelates were opposed to the Jesuits. It is now known that even Bossuet, who sternly opposed the Jesuits, had his secret amours, and there were, on the other hand, men of ascetic life, if not very clear intelligence (like Vincent de Paul), on the side of the Jesuits. However, the open declaration of so large and powerful a body of the clergy exasperated the Jesuits, and the war of sermons and pamphlets reached a stage of incandescence. Father Nouet denounced Arnauld as "fantastic, melancholic, lunatic, blind, malicious, furious," and showered upon him such concrete epithets as serpent, scorpion, wolf, and monster. Arnauld had ventured to say that sinful ladies must keep away from the Holy Sacrament. But Father Nouet went on to assail the sixteen prelates who had approved Arnauld's book, and this led to his undoing. To their great mortification the Jesuit superiors were forced to disavow and reprimand their preacher, and the Jansenists triumphed. The Jesuits retorted, however, by intrigue at the court, and induced Mazarin and the Queen-Regent to order Arnauld to go and defend his book at Rome. This was a violation of the rights of the Gallican Church, and the university, the Parlement, and the clergy protested so violently that the project had to be abandoned.

St. Cyran had died in the meantime (in 1643) and Arnauld was leader of the growing and powerful body of Puritans. As the next move of the Jesuits at court would be to secure a lettre de cachet, and lodge him in the Bastille or Vincennes, he returned to the provinces and the struggle was transferred to Rome. The prelates who had approved Arnauld's book appealed to the Pope in its favour, and a learned theologian was sent to Rome to defeat the manœuvres of the Jesuits. As a result, after two years of violent discussion, the book was declared free of heresy. The Jesuits, who had declared that thirty propositions in the book were unsound, now concentrated upon an innocent parenthetic phrase in the preface. Arnauld had referred to Peter and Paul as "two chiefs who were really one," and it was claimed that this was an attack on the papacy. After another year of wrangling and intrigue the innocuous sentence was condemned, and the Jesuits proclaimed throughout Europe that they had triumphed.

The next step was to enforce in France the bull of Urban VIII. condemning the Augustinus of Jansen. The Sorbonne (the theological school of the university) received a papal brief directing them to accept the bull, and, in spite of court-pressure, the theologians justly replied that they were not concerned with the opinions of a Belgian theologian. Again the pulpits of Paris—the artillery of the spiritual army—opened fire, and the pamphleteers were busy. Then the syndic of the Sorbonne, Cornet, a friend of the Jesuits, submitted seven propositions to the judgment of that body. He named no author, and expressly (and mendaciously) stated that they did not refer to Jansen, but it was well known that the sentences were supposed to have been extracted from the work of Jansen, and an intense struggle followed. The cause was won, as usual, by intrigue. There was some dispute at the time how far the monastic theologians could vote at the Sorbonne, but they were brought up in force, against the view of the lawyers, and five propositions were condemned and reported to Rome. It was now openly stated that the five propositions were taken from Jansen's book.

The Papacy still hesitated, in view of the disputable nature of the Sorbonne vote, and intimated that the French prelates should be induced to ask for a condemnation. According to M. Crétineau-Joly, the reply was prompt and spontaneous. "The General Assembly of the clergy opens at Paris, and eighty-eight bishops denounce the five propositions to Pope Innocent"; the Jesuits, he says, stood aside and let the prelates speak. But the French historian must have been aware that the question was not submitted to the General Assembly at all. The signatures were obtained privately, and the whole procedure was so insidious that we are not sure to-day whether seventy, or eighty, or ninety bishops demanded a condemnation. It is necessary to note these details, if we are to understand the Catholic sentiment which later swept the Jesuits out of France. About eighty bishops apparently were induced privately to request the Pope to condemn the propositions; other prelates wrote to beg the Pope to abstain. However, the Vatican was now officially invited to pronounce, and the war of theologians was resumed at Rome.

In the meantime the Jesuits of Paris sustained a painful check in their attack on the Jansenists. One of their number, Father Brisacier, published a pamphlet, Le Jansenisme confondu (1651), in which, not only were the familiar invectives showered upon the Solitaries, but the moral character of the nuns of Port Royal was attacked. These were the nuns whom a hostile archbishop afterwards declared to be "as pure as angels and as proud as devils." The purity of their lives was notorious, and intense indignation was felt. The Archbishop of Paris formally condemned the pamphlet as "containing many lies and impostures," and Father Brisacier was removed—promoted to the rectorship of the college at Rouen—by his superiors. No Jesuit, of course, wrote without authorisation, and the many abominable pamphlets they issued at this time against the Puritans implicate the whole Parisian Province.

We need not follow the course of the trial at Rome. After a two years' struggle Innocent X. issued his famous bull in which the five propositions were declared to be heretical, and to be contained in the work of Jansen. The Jesuits emitted a pyrotechnic discharge of oratory and pamphlets—one broadside of the time represented Bishop Jansen as a devil flying to the Protestants—but they had overreached themselves. No Jansenist (not even Jansen) had ever taught the five propositions, and there was not a man in France who wished to defend them. But the Jesuits had insisted on the pronouncement that the propositions were contained in Jansen, and this gave rise to a formidable controversy in which the prelates were at liberty to join. It may seem to the modern reader an appalling waste of energy and perversion of character that so powerful a body should spend their resources for twenty years in a war on such abstruse propositions, but from this point the struggle becomes frankly ridiculous. For nearly eighty years we shall find the Jesuits straining every device of craft and learning to ensure that every man in France shall agree that the Pope (who had never read Jansen's book) was right in declaring the five propositions to be contained in the Augustinus; and the controversy they sustain will draw on themselves the appalling scourge of Pascal's Provincial Letters and on the papacy the defiant declaration of the Gallican Church. We are compelled to recognise a lamentable corporate ambition and perversion of character in their conduct.

The Puritans coolly replied that they were not interested in the five propositions which the Pope had condemned, but that, as a matter of plain truth, they must protest against the ascription of these views to Bishop Jansen. So the war proceeded. It was at this time, in 1654, that the Jesuits made a ludicrous attempt to discredit their opponents by revealing the famous "Plot of Bourg Fontaine": a plot as rich in imagination and crude in fictitious detail as the Titus Oates plot. They had discovered, they gravely reported, that St. Cyran, Arnauld, and four other Jansenists had, twenty-three years before, met secretly in an obscure village to concert a plot for the destruction of Christianity in France. Arnauld was nine years old at the time given as the year of the conspiracy. Arnauld, from his solitude, issued a letter against the Jesuits, and (again packing the jury with monk-voters) they got it condemned by the Sorbonne. When we find the King writing to press the Sorbonne, we may clearly recognise the hand of the court-Jesuits. They triumphed, but their triumph now drew on them the heaviest and most enduring punishment they have ever suffered.

In 1648 the nuns had been compelled to return from Paris to their inhospitable valley, and the Solitaries had retreated from the abbey to a manor-house on the hill overlooking the valley. There, without any special costume or vows, a number of the most brilliant young men of Paris led a life of great austerity and devotion. Some lived in Paris, and spent an occasional period at Les Granges, and amongst these was a young man, with thin, pale face and large brilliant eyes under his lofty forehead, named Blaise Pascal. He had already won European fame as a mathematician. When Arnauld, somewhat jaded, produced a weak reply to his opponents, his friends suggested that Pascal should be asked to undertake the attack. Arnauld agreed, and on 23rd January 1656, appeared the first Letter to a Provincial. It was a subtle and irresistible satire of the theological shibboleths of the Jesuits. In order to enable the conflicting schools of monastic theology to agree in condemning the Jansenists, certain terms (such as "proximate grace" and "sufficient grace") had been introduced as vague common measures of orthodoxy, and Pascal expended his immortal wit on the weakness. It is admitted by all that the earlier Provincial Letters are masterpieces of satire. The letter was received with delight in Paris, and a week later, while the debate continued at the Sorbonne, a second letter was issued. The third appeared ten days later, after the censure of Arnauld.