Question I: What heresy is

The NAME of Heresy has its origin from eligo, in Greek αἵρεσις, and it signifies an Opinion which one voluntarily and pertinaciously elects for himself, as they commonly teach with D. Bonav. here. Whence it is also called a Sect, because we follow it; and in that sense the various sects of the Philosophers were so called, because, withdrawing from the common body, they erected new Schools, as S. Bonaventura says here.

But the name of Sect was once in a good sense, as Act. 24. et 26. Now however the name of sect must be abstained from for indicating our religion, as Suarez says disp. 19. sect. 2. Lugo disp. 20. sect. 1. because it avails for expressing only alien religions, as Beda notes ad 24. Act. and we now call heretics Sectaries, and we derive sect not from following, but from persecuting, as S. Doct. notes here.

Heresy is DEFINED: Est error, fidei Catholicae contrarius, cui pertinaci animo inhaereat is, qui est professus fidem in Baptismo. It is an error contrary to the Catholic faith, to which he who has professed the faith in Baptism adheres with pertinacious mind. Thus Turrecremata defines it, lib. 4. Summae, p. 2. cap. 1. from the common mind of the Doctors in 4. dist. 13. where D. Bonav. dub. 4. D. Thom. quaest. 11. art. 2. ad 3. and his Interpreters. And more safely D. Bonau. in speculo animae, cap. 1. and p. 1. Centil. sect. 26. But in the former place D. Bonau. defines a heretic in these words: Haereticus est qui divinae legis ignorantia, vel contemptu, pertinax inventor proprii erroris, aut alieni sectator, Catholicae veritati mavult adversari, quam subiici. A heretic is he who, through ignorance or contempt of the divine law, a pertinacious inventor of his own error or a follower of another's, would rather oppose the Catholic truth than submit to it. Concerning this definition many questions occur.

The FIRST is: Whether error from ignorance is heresy: whether doubt, or merely probable assertion about matters of faith is heresy. What pertinacity is required for heresy: Whether it is required for heresy that it be in a baptized person, and other similar questions, which we shall run through.

Meanwhile I note that heresy is divided into Formal, and Objective. Formal is that actual sin by which someone is formally denominated a heretic: Objective indeed is the object which is falsely believed or asserted by the heretic, v. g. that Christ is not God, etc.