Lessons on the psychology of heresy from Pius VI's Auctorem Fidei

The papal Bull Auctorem Fidei was Pope Pius VI's Constitution against the Errors of the Synod of Pistoia (1786) in Italy. Those errors consisted of the Gallican and Jansenist acts and tendencies represented by the Synod, a tapestry of novelties introduced under the veil of ambiguity, distortion, and obfuscation. The former Bishop of Pistoia, Scipione de' Ricci, is said to have "embarked on confusing, destroying, and utterly overturning [sound Christian doctrine] by introducing troublesome novelties under the guise of a sham reform."

The document has been repeatedly cited by later Popes when called to combat doctrinal errors in the 19th and 20th centuries. It is mentioned in Indulgentiarum Doctrina, Quo Graviora, Commissum Divinitus, Mysterium Fidei and Pascendi Dominici Gregis.

The introductory part of this Bull (advisory: see Rules 7-9)makes for instructive reading because of the uncanny clarity with which Pius VI describes the psychology of the heretical mind and its methods (emphasis Mundabor's):

They [ our most holy predecessors] knew the capacity of innovators in the art of deception. In order not to shock the ears of Catholics, the innovators sought to hide the subtleties of their tortuous maneuvers by the use of seemingly innocuous words such as would allow them to insinuate error into souls in the most gentle manner. Once the truth had been compromised, they could, by means of slight changes or additions in phraseology, distort the confession of the faith that is necessary for our salvation, and lead the faithful by subtle errors to their eternal damnation. This manner of dissimulating and lying is vicious, regardless of the circumstances under which it is used. For very good reasons it can never be tolerated in a synod of which the principal glory consists above all in teaching the truth with clarity and excluding all danger of error. Moreover, if all this is sinful, it cannot be excused in the way that one sees it being done, under the erroneous pretext that the seemingly shocking affirmations in one place are further developed along orthodox lines in other places, and even in yet other places corrected; as if allowing for the possibility of either affirming or denying the statement, or of leaving it up the personal inclinations of the individual – such has always been the fraudulent and daring method used by innovators to establish error. It allows for both the possibility of promoting error and of excusing it. It is a most reprehensible technique for the insinuation of doctrinal errors and one condemned long ago by our predecessor St. Celestine, who found it used in the writings of Nestorius, bishop of Constantinople, and which he exposed in order to condemn it with the greatest possible severity. Once these texts were examined carefully, the impostor was exposed and confounded, for he expressed himself in a plethora of words, mixing true things with others that were obscure; mixing at times one with the other in such a way that he was also able to confess those things which were denied while at the same time possessing a basis for denying those very sentences which he confessed.

What methods does Pius use to expose the error?

In order to expose such snares, something which becomes necessary with a certain frequency in every century, no other method is required than the following: Whenever it becomes necessary to expose statements that disguise some suspected error or danger under the veil of ambiguity, one must denounce the perverse meaning under which the error opposed to Catholic truth is camouflaged.

[Hat tip to S. Armaticus via JM]