The Pelagians asserted that man works out his eternal salvation of his own free will, and that consequently God merely foreknows but does not fore-ordain who shall be saved. The Semipelagians held that the beginning of faith (_initium fidei_) and final perseverance (_donum perseverantiae_) are not pure graces but may be obtained by natural means, without special aid from above. Against these heretics the Catholic Church has always taught the eternal predestination of the elect as an article of faith.(579)
a) St. Paul says explicitly: “We know that to them that love God, all things work together unto good, to such as, according to his purpose, are called to be saints. For whom he foreknew, he also predestinated to be made conformable to the image of his Son; that he might be the firstborn amongst many brethren. And whom he predestinated, them he also called. And whom he called, them he also justified. And whom he justified, them he also glorified.”(580) Here we have all the elements of complete predestination: God’s eternal foreknowledge (_praescivit_, προέγνω), an eternal decree of the divine will (_praedestinavit_, προώρισε), and the various stages of justification, beginning with vocation (_vocavit_, ἐκάλησε) up to justification proper (_iustificavit_, ἐδικαίωσε), and eternal beatitude (_glorificavit_, ἐδόξασεν).(581)
b) The Fathers of the fifth century undoubtedly taught the predestination of the elect as an article of faith. Thus St. Augustine says: “There never was a time when the Church of Christ did not hold this faith in predestination, which is now defended with fresh solicitude against the new heretics.”(582) His faithful disciple St. Prosper writes: “No Catholic denies predestination by God.”(583) And again: “It would be as impious to deny predestination as to oppose grace itself.”(584)
c) Several important theological corollaries follow from the dogma of predestination.
α) The first is the immutability of the divine decree of predestination. This immutability is based on God’s infallible foreknowledge that certain individuals will die in the state of grace, and on His unchangeable will to reward them with eternal happiness.
St. Augustine says: “If any one of these [the predestined] perishes, God is mistaken; but none of them perish because God is not mistaken.”(585)