The quoted article is wrong. On the subject of eternal security, once saved always saved or perseverance of the saints, Paul does not teach Calvinism, Calvin interprets Paul and other Scriptures. Where you agree with the 5 point of Calvinism or not the Pauline teaching on Security agrees with word's of Jesus Christ:
John 3:16 For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
Everlasting life began when whosoever believes and cannot end or it will not be everlasting.
John 6:37 All that the Father giveth me shall come to me; and him that cometh to me I will in no wise cast out.
Praise the Lord, Jesus Christ will never get sick of us and throw us out.
John 10:28 And I give unto them eternal life; and they shall never perish, neither shall any man pluck them out of my hand. 29 My Father, which gave them me, is greater than all; and no man is able to pluck them out of my Father’s hand.
Eternal life carries with it the promise of Jesus Christ and God the Father to hold onto His children. It also carries the promise of being kept from perishing. The idea that when we put ourselves into God's hand we can take ourselves out forgets that we constantly make decisions which we may regret but have no power to change. I have never regretted trusting the Lord to save me.
Hebrews 13:5 Let your conversation be without covetousness; and be content with such things as ye have: for he hath said, I will never leave thee, nor forsake thee. 6 So that we may boldly say, The Lord is my helper, and I will not fear what man shall do unto me.
The writer of Hebrews shares the 4th promise Jesus Christ will not leave or forsake us. The warning is clear regardless of how faithful we live, Jesus will not leave us, He will help us!
These are my personal interpretations and I acknowledge I could be wrong! I am not a Calvinist or and Arminianist, I follow Jesus Christ.
While these Scriptures have elements that some may call Calvinistic. To me they are simple the promises of my loving Lord and Savior. I trust Him to keep His Word and I don't have to know or explain how it all works out. He is Lord not me.
When my children were small we would walk across a busy parking lot and I would hold out my little finger and say, "Hold my hand as we go across the parking lot".The would grab my finger in their little hand and I would wrap my hand around theirs. The thought their safety depended on their grip, I KNEW their safety depended on MY GRIP! I didn't lose any of them.