Having moved past the initial arguments for the present author’s position, there still remains the task of showing that St. Paul was thoroughly Catholic in other areas. One of the areas mentioned in part 1 was that St. Paul taught, as the Catholic Church teaches, that it is possible for the man who has been justified to fall from that state of grace and therefore forfeit his own salvation.
In parts 2 and 3 the author presented a number of Pauline passages to show that “faith alone”, unless it be understood in an orthodox Catholic sense, does not save. These same passages (Galatians 6: 7-8, Romans 2:6-10, 2 Corinthians 5:10) prove that those who have been justified are not guaranteed a place in heaven, as many Protestant brethren would claim (including the author’s beloved family member mentioned along the way.) There are other passages of St. Paul that prove Catholic teaching.
In Romans chapter 8 St. Paul warns that those who live according to the flesh shall die (verse 13).  In chapter 13, he explains that the Gentiles have become grafted onto the olive tree as wild branches. He teaches that some of the natural branches have been broken off through their unbelief (i.e. the unbelieving Jews.) He then goes on to warn his Gentile Christian audience that they must not be high-minded, “…For if God hath not spared the natural branches, fear lest perhaps he also spare not thee.” (Verses 20-21).  Then, when discussing the goodness and the severity of God, he warns his readers that if they do not abide in goodness they too shall be cut off (verse 22.)  One can infer from the text that those who do not abide in goodness will share the lot of the unbelieving Jews (i.e. they will be “cut off.”) And this is only the first Book in the Bible written by St. Paul.
In 1 Corinthians chapter 3, after telling his audience that they are the temple of God and that the Holy Spirit dwells in them (verse 16), he tells them that God will destroy anyone who violates the temple of God (verse 17.) In chapter 6 he warns the Corinthians of sins that [can] exclude one from the kingdom of God (verses 9-10.) In chapter 10 he warns that “…he that thinketh himself to stand, let him take heed lest he fall.” (Verse 12.)  Commenting on this verse, St. John Chrysostom writes that “…our standing here is not secure standing, no not until we be delivered out of the waves of this present life and have sailed into the tranquil haven. Be not therefore high-minded at your standing, but guard against your falling; for if Paul feared who was firmer than all, much more ought we to fear.” (“Homily 23 on First Corinthians.”)  And there is more.
Passages similar to 1 Corinthians6: 9-10 are found in St. Paul’s Epistles to the Galatians:
 Now the works of the flesh are manifest, which are fornication, uncleanness, immodesty, luxury,  Idolatry, witchcrafts, enmities, contentions, emulations, wraths, quarrels, dissensions, sects,
 Envies, murders, drunkenness, revellings, and such like. Of the which I foretell you, as I have foretold to you, that they who do such things shall not obtain the kingdom of God. (Chapter 5.) (Emphasis mine.)
And also to the Ephesians:
 For know you this and understand, that no fornicator, or unclean, or covetous person (which is a serving of idols), hath inheritance in the kingdom of Christ and of God. (Chapter 5) 
Finally, in his “Epistle to the Philippians”, St. Paul urged his readers to work out their salvation with fear and trembling ( chapter 2:12.)  He sent Timothy to the Thessalonians (in part) to know their faith and whether or not his and others’ work had been “made vain” through their being tempted by the tempter (1 Thessalonians 3:5.)  He told Timothy that some had “made shipwreck concerning the faith” (1 Timothy 1:19) , and concerning Christ that “If we deny him, he will also deny us .” (2 Timothy 2:12.) 
More evidence could be cited, especially from the “Epistle to the Hebrews.” If one is hesitant to attribute this Epistle to him, “No valid reason has been produced against Paul as the originator of the ideas and the entire contents of the letter; the belief of the early Church held throughout with entire correctness to this Apostolic origin of the Epistle.” 
In the next article the present author will show other Catholic teachings that can be proven by the writings of St. Paul.
http://www.drbo.org/chapter/52008.htm (accessed 12/26/2011)
http://www.drbo.org/chapter/52011.htm (accessed 12/26/2011)
Regarding the phrase “Otherwise thou also shalt be cut off” in verse 22, the footnote in the Douay-Rheims Catholic Bible points out that this is in reference to individual Christians as opposed to the Church which can never fall from Christ according to Scripture. (Ibid.)
http://www.drbo.org/chapter/53003.htm (accessed 12/26/2011)
The present author adds the caveat here “can” because he has in mind exceptions such as the following: the 3 conditions which must exist for a sin to be mortal, restoration to the state of grace by an act of perfect contrition with the purpose of going to the Sacrament of Reconciliation as soon as possible, or, the Sacrament of Reconciliation. Also, the possibility of later receiving the Sacrament of Baptism and exceptions that may or may not exist for non-Catholics.
http://www.drbo.org/chapter/53006.htm (accessed 12/26/2011)
http://www.drbo.org/chapter/53010.htm (accessed 12/26/2011)
http://www.newadvent.org/fathers/220123.htm (accessed 12/26/2011)
http://www.drbo.org/chapter/55005.htm (accessed 12/26/2011) (Emphasis mine.)
http://www.drbo.org/chapter/56005.htm (accessed 12/26/2011)
http://www.drbo.org/chapter/57002.htm (accessed 12/26/2011)
http://www.drbo.org/chapter/59003.htm (accessed 12/26/2011)
http://www.drbo.org/chapter/61001.htm (accessed 12/26/2011)
http://www.drbo.org/chapter/62002.htm (accessed 12/26/2011)
Fonck, Leopold. “Epistle to the Hebrews.” The Catholic Encyclopedia. Vol. 7. New York: Robert Appleton Company, 1910. 26 Dec. 2011 <http://www.newadvent.org/cathen/07181a.htm>.