The Unalterable Perseverance Of The Saints?

When we show Calvinists passages that plainly say those in sin will be lost (e.g., Rev 21:8) and therefore Christians who fall back into sin will lose their salvation, many respond by saying when a person falls back into sin, that proves they were never saved to being with.But this theory would mean David (adultery and murder, II Sam 11:3-4,12:9), Noah (drunkenness, Gen 9:20-21), and Peter (denying Christ, Matt 26:69-75) were never saved to begin with. And Calvinists certainly don’t believe that, so they are inconsistent to say the very least.And notice the following passages that teach it is possible for a truly born again person to fall …According to John 15:1-6, it is possible for those “in” Christ and “clean through the word” (Christians) to quit abiding in Jesus, to quit bearing fruit, and to be taken away and burned (an allusion to h-e-l-l).Gal 4:5-6,5:4 teaches “sons” (of God) with the Holy Spirit in their hearts (Christians) can be “severed from Christ” (ASV) and “fallen from grace.”Heb 3:1,12 proves “holy brethren, partakers of the heavenly calling” (Christians) can develop an “evil heart of unbelief … departing from … God.”James 5:19 says “brethren” (Christians) can “err from the truth.”II Pet 1:9 shows one who is “purged from his old sins” (Christians) can get to a point where he “lacketh these things (the Christian graces), is blind, and cannot see.”II Pet 2:1,20-22 talks about those whom the Lord “bought” and had “escaped the pollutions (sins) of the world through the knowledge of … Christ” through being “washed” (Christians) - becoming “false teachers” who “bring in condemnable heresies … denying the Lord” and become “entangled again in ... sins of the world and overcome.”And Rev 22:19 refers to those who were a “part … of the book of life” (Christians) being taken “out of the book of life.”So clearly a born again person can go back into sin. And if he does, he “shall not inherit the kingdom of God” (Gal 5:19-21).