  During the night of 23 November 1654, Pascal had a dreamlike or ecstatic experience which he interpreted as a religious conversion. He wrote a summary of the experience in a brief document entitled the Memorial, which he sewed into his coat and carried with him until his death eight years later. The intensity of this experience resulted in a definitive change in Pascal's lifestyle, in his intellectual interests, and in his personal ambitions. After 1654, he terminated the mathematical discussions about which he had correspondended with Fermat, and he cancelled plans to publish a booklet on the vacuum that was ready to go into print. This booklet appeared posthumously as Traités de l'équilibre des liqueurs et de la pesanteur de la masse de l'air (1663), with an introduction by Florin Périer. Périer may have exaggerated the other-worldly attitude of his late brother-in-law, when he wrote that, for more than ten years before his death, Pascal was aware of “the vanity and nothingness of all these types of knowledge, and that he had acquired such disgust for them that he could hardly tolerate intelligent people devoting their time to them and speaking seriously about them” (I, 459). Pascal had entered the final period of his life, which was dominated by religious controversy, continual illness, and loneliness. This was also the period in which he assumed the challenge of defending Arnauld and, more generally, Jansenist theology in the Provincial Letters.