To be more extensive with my question:
How does the Church determine what is heresy, and more specifically, the difference between that, schism, and apostasy?
I know that some beliefs have historically been declared heretical by ecumenical councils in the past (like the Church’s dealing with Arius’s misleading brand of “subordinationism”).
I didn’t feel that this belonged in Apolgetics, as it’s less of a divine question.
Thanks, and God bless!
Modern Catholic Dictionary:
HERESY. Commonly refers to a doctrinal belief held in opposition to the recognized standards of an established system of thought. Theologically it means an opinion at variance with the authorized teachings of any church, notably the Christian, and especially when this promotes separation from the main body of faithful believers.
In the Roman Catholic Church, heresy has a very specific meaning. Anyone who, after receiving baptism, while remaining nominally a Christian, pertinaciously denies or doubts any of the truths that must be believed with divine and Catholic faith is considered a heretic. Accordingly four elements must be verified to constitute formal heresy; previous valid baptism, which need not have been in the Catholic Church; external profession of still being a Christian, otherwise a person becomes an apostate; outright denial or positive doubt regarding a truth that the Catholic Church has actually proposed as revealed by God; and the disbelief must be morally culpable, where a nominal Christian refuses to accept what he knows is a doctrinal imperative.
Objectively, therefore, to become a heretic in the strict canonical sense and be excommunicated from the faithful, one must deny or question a truth that is taught not merely on the authority of the Church but on the word of God revealed in the Scriptures or sacred tradition. Subjectively a person must recognize his obligation to believe. If he acts in good faith, as with most persons brought up in non-Catholic surroundings, the heresy is only material and implies neither guilt nor sin against faith. (Etym. Latin haeresis, from the Greek hairesis, a taking, choice, sect, heresy.)
SCHISM. A willful separation from the unity of the Christian Church. Although St. Paul used the term to condemn the factions at Corinth, these were not properly schismatical, but petty cliques that favored one or another Apostle. A generation later Clement I reprobated the first authentic schism of which there is record. Paul’s exhortation to the Corinthians also gives an accurate description of the concept. “Why do we wrench and tear apart the members of Christ,” he asks, “and revolt against our own body, and reach such folly as to forget that we are members of one another?” While the early Church was often plagued with heresy and schism, the exact relation between the two divisive elements was not clarified until later in the patristic age. “By false doctrines concerning God,” declared St. Augustine, “heretics wound the faith; by sinful dissensions schismatics deviate from fraternal charity, although they believe what we believe.” Heresy, therefore, by its nature refers to the mind and is opposed to religious belief, whereas schism is fundamentally volitional and offends against the union of Christian charity. (Etym. Latin schisma; from Greek skhisma, a split, division, from skhizein, to tear, rend.)
APOSTASY. The total rejection by a baptized person of the Christian faith he once professed. The term is also applied in a technical sense to “apostates from religious life,” who without authorization leave a religious institute after perpetual vows with no intention of returning. (Etym. Latin apostasia, falling away or separation from God; from Greek apostasis, revolt, literally, a standing-off.)
