"... a heretic who obstinately disbelieves one article of faith is not prepared to follow the teaching of the Church in all things. But if he is not obstinate, he is no longer in heresy but only in error. Therefore it is clear that such a heretic with regard to one article of faith has no faith in the other articles, but only a kind of opinion in accordance with his own will."
~St. Thomas Aquinas: Summa Theologica, II-II, q. 5, a. 3.
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