This ‘nuit de feu’ was such that Pascal sewed the record that he made of it at the time of the event itself as a permanent memento into his clothes, where it was found at his death. The document records an experience of conversion; not an intellectual experience, but one which persuaded Pascal of the superiority of instinctive belief. (This conviction was strengthened two years later, when his niece was cured miraculously at Port-Royal of an apparently incurable fistula.)
As a result of his experience, Pascal went to Port-Royal-des-Champs for a two-week retreat in 1655. There he met Isaac Le Maistre de Saci, a Jansenist theologian, with whom he had a debate, an account of which was published in 1720 as Entretien avec M. de Saci (A conversation with M. de Saci). This debate indicates not only that Pascal had conceived of an apology of the Christian religion in terms which would speak most powerfully to the very libertines and gamblers of the Parisian society which he had just forsaken, but also that he felt that one of the most powerful voices with which he had to contend was that of Michel de Montaigne, the gentleman philosopher who had championed the cause of scepticism in the later sixteenth century.
It is also clear that he felt the need to reassure those who had been shaken in their faith by new scientific developments, especially those in astronomy. Among Pascal’s immediate sources of inspiration was Antoine Arnauld, the leading Jansenist theologian and philosopher, who was at that time on the point of being condemned by the Sorbonne for his religious views. Together with Arnauld and Pierre Nicole, another prominent Jansenist, Pascal composed the Lettres provinciales (Provincial letters), a series of eighteen letters published in 1656-7.