Complex sentence: During the formulary controversy which opposed Jesuits to Jansenists concerning the orthodoxy of Jansenius' propositions, Arnauld was forced to go into hiding after a motion of censorship voted against him at the Sorbonne, which prompted Pascal to anonymously write the "Provincial Letters".
Split into simpler sentences: During the formulary controversy which opposed Jesuits to Jansenists concerning the orthodoxy of Jansenius' propositions, Arnauld was forced to go into hiding. This motion prompted Pascal to anonymously write the "Provincial Letters".