The casuistic method was popular among Catholic thinkers in the early modern period, and not only among the Jesuits, as it is commonly thought. Famous casuistic authors include Antonio Escobar y Mendoza, whose Summula casuum conscientiae (1627) enjoyed a great success, Thomas Sanchez, Vincenzo Filliucci (Jesuit and penitentiary at St Peter’s), Antonino Diana, Paul Laymann (Theologia Moralis, 1625), John Azor (Institutiones Morales, 1600), Etienne Bauny, Louis Cellot, Valerius Reginaldus, Hermann Busembaum (d. 1668), etc. One of the main theses of casuists was the necessity to adapt the rigorous morals of the Early Fathers of Christianity to modern morals, which led in some extreme cases to justify what Innocent XI later called “laxist moral” (i.e. justification of usury, homicide, regicide, lying through “mental reservation”, adultery and loss of virginity before marriage, etc.—all due cases registered by Pascal in the Provincial Letters).
The progress of casuistry was interrupted toward the middle of the 17th century by the controversy which arose concerning the doctrine of probabilism, which stipulated that one could choose to follow a “probable opinion”, that is, supported by a theologian or another, even if it contradicted a more probable opinion or a quotation from one of the Fathers of the Church.[19] The controversy divided Catholic theologians into two camps, Rigorists and Laxists.
Casuistry was much mistrusted by early Protestant theologians, because it justified many of the abuses that they sought to reform. It was famously attacked by the Catholic and Jansenist philosopher Pascal, during the formulary controversy against the Jesuits, in his Provincial Letters as the use of rhetorics to justify moral laxity, which became identified by the public with Jesuitism; hence the everyday use of the term to mean complex and sophistic reasoning to justify moral laxity.[20] By the middle of the 18th century, “casuistry” became a synonym for moral laxity.[citation needed]
In 1679 Pope Innocent XI publicly condemned sixty-five of the more radical propositions (stricti mentalis), taken chiefly from the writings of Escobar, Suarez and other casuists as propositiones laxorum moralistarum and forbade anyone to teach them under penalty of excommunication.[21] Despite this papal condemnation, both Catholicism and Protestantism permit the use of ambiguous and equivocal statements in specific circumstances.[22]
Alphonsus Maria de Liguori (d. 1787), founder of the Congregation of the Most Holy Redeemer, then brought some attention back to casuistry by publishing again Hermann Busembaum’s Medulla Theologiae Moralis; the last edition published in 1785 and receiving the approbation of the Holy See in 1803.[citation needed] Busembaum’s Medulla had been burnt in Toulouse in 1757 because of its justification of regicide, deemed particularly scandalous after Damiens’ assassination attempt against Louis XV.[citation needed]
Casuistry in early modern times