Frederick Copleston, in his A History of Philosophy, critiques [pre- Voltaire and Jean-Jacques Rousseau] Pascal's attacks on the Jesuits and casuistry: "He selects for mention and condemnation extreme cases of moral accommodation from certain authors, and he tends to confuse casuistry itself with the abuse of it. Furthermore, he tends to attribute to moral theologians unworthy motives which were certainly absent from their minds". He felt that the letters exhibited a "failure to distinguish between the fundamental and valid principles of moral theology and the abuse of casuistry". However he added that "for good measure he accused the Jesuits of hypocrisy. In one sense he got the better of the dispute. For he was a brilliant writer, whereas his opponents did not produce any answer which was capable of having an effect equal".[18]

https://en.wikipedia.org/wiki/Lettres_provinciales 

The reaction to the Lettres provinciales was substantial. Pascal's use of wit, humor, and mockery in attacking existing institutions made his work extremely popular. However, its publication was primarily via the underground press, and in 1660 Louis XIV banned the book and ordered it shredded and burned.^{[citation needed]} The Church banned it by placing on the Index Librorum Prohibitorum.^[a] Pascal himself had to enter clandestinity, living in cheap hostels. Nevertheless, the letters survived and influenced the prose of later French writers like Voltaire and Jean-Jacques Rousseau. The extract of the Seventh Letter concerning the "direction of intention" influenced Molière's Tartuffe (Act IV, scene V, 1489–1493).

According to his niece Marguerite Périer, Pascal later said that he did not regret publishing the letters, and if he were to do it again he would write more forcefully.^[13] He defended the style in which he wrote the letters, explaining that "if I had written dogmatically, my papers would have been only read by the learned, and those who had no need of the information I furnished".^[14]

Rufus Suter has stated that the letters became "the model for the satirical essay in French" and have become "the only legacy of Jansenism that continue to inspire the religious imagination".^[15] Voltaire wrote that "All types of eloquence are contained in these letters." He also called them "the best-written book that has yet appeared in France."^[16] When Jacques-Bénigne Bossuet was asked what book he would rather have written had he not written his own, he answered, the Provincial Letters of Pascal.^[17]