Here’s Jimmy Akin’s article on “Reformed” doctrine:
cin.org/users/james/files/tulip.htm
**Perseverance of the saints **
Calvinists teach that if a person enters a state of grace he never will leave it but will persevere to the end of life. This doctrine is normally called the perseverance of the saints. [33] All those who are at any time saints (in a state of sanctifying grace, to use Catholic terminology) will remain so forever. No matter what trials they face, they will always persevere, so their salvation is eternally secure. [34]
Analogies are used to support this teaching. Calvinists point out that when we become Christians we become God’s children. They infer that, just as a child’s position in the family is secure, our position in God’s family is secure. A father would not kick his son out, so God will not kick us out.
This reasoning is faulty. The analogy does not prove what it is supposed to. Children do not have “eternal security” in their families. First, they can be disowned. Second, even if a father would not kick anyone out, a child can leave the house on his own, disown his parents, and sever all ties with the family. Third, children can die; we, as God’s children, can die spiritual deaths after we have been spiritually “born again.” [35]
Calvinists also use Bible passages to teach perseverance of the saints. The chief ones are John 6:37-39, 10:27-29, and Romans 8:35-39. The Calvinist interpretation of these passages takes them out of context [36], and there are numerous other exegetical problems with their interpretation. [37]
Calvinists assume perseverance of the saints is entailed by the idea of predestination. If one is predestined to be saved, does it not follow he must persevere to the end?
This involves a confusion about what people are predestined to: Is it predestination to initial salvation or final salvation? **The two are not the same. A person might be predestined to one, but this does not mean he is predestined necessarily to the other. [38] One must define which kind of predestination is being discussed. **
If one is talking about predestination to initial salvation, then the fact that a person will come to God does not of itself mean he will stay with God. If one is talking about predestination to final salvation, then a predestined person will stay with God, but this does not mean the predestined are the only ones who experience initial salvation. Some might genuinely come to God (because they were predestined to initial salvation) and then genuinely leave (because they were not predestined to final salvation). [39] Either way, predestination to initial salvation does not entail predestination to final salvation. [40] **There is no reason why a person cannot be predestined to “believe for a while” but “in time of temptation fall away” (Luke 8:13). [41] **
A Catholic must affirm that there are people who experience initial salvation and who do not go on to final salvation, but he is free to hold to a form of perseverance of the saints. The question is how one defines the term “saints”–in the Calvinist way, as all those who ever enter a state of sanctifying grace, or in a more Catholic way, as those who will go on to have their sanctification (their “saintification”) completed. [42] If one defines “saint” in the latter sense, a Catholic may believe in perseverance of the saints, since a person predestined to final salvation must by definition persevere to the end. Catholics even have a special name for the grace God gives these people: “the gift of final perseverance.”
The Church formally teaches that there is a gift of final perseverance. [43] Aquinas (and even Molina) said this grace always ensures that a person will persevere. [44] Aquinas said,
“Predestination [to final salvation] most certainly and infallibly takes effect.” [45] But not all who come to God receive this grace.
**Aquinas said the gift of final perseverance is “the abiding in good to the end of life. In order to have this perseverance man…needs the divine assistance guiding and guarding him against the attacks of the passions…[A]fter anyone has been justified by grace, he still needs to beseech God for the aforesaid gift of perseverance, that he may be kept from evil till the end of life. For to many grace is given to whom perseverance in grace is not give.” [46] **