If you believe that salvation can be lost...
Why were the apostles sure that they would go to Heaven, even though they still had time to sin (2 Timothy 4:18, 1 Peter 5:1, 2 John 2-3)?
Why did the apostles want the believers to whom they wrote to be sure of their future in Heaven (Romans 5:9, 1 Corinthians 1:8, Philippians 3:20-21, 1 Peter 1:3-5, 5:4, 1 John 5:13, 2 John 2-3)?
Critics of eternal security argue that salvation depends on our present faith and our present behavior. Why, then, do the scriptures refer to people having salvation, or something associated with salvation, in the present because of a past faith or a past justification (Luke 7:50, Acts 19:2, Romans 5:1)? How is this possible if there isn't a moment of faith in the past that results in our future salvation?
Why do the scriptures say that salvation is a free gift of God's grace (Romans 3:24, 5:17, 6:23, Revelation 22:17)? If attaining salvation through works would contradict grace (Romans 4:4, 11:6), then how can maintaining salvation through works be consistent with grace? If I give you a car, and tell you that it's a "free gift", but then I send you monthly bills for it thereafter, was the car really a "free gift"?
Why does Paul write, "where there is no law, neither is there violation...For sin shall not be master over you, for you are not under law, but under grace" (Romans 4:15, 6:14), as well as emphasizing elsewhere that once a person becomes a Christian he is no longer under any law of works (Romans 5:13, 10:4, 1 Corinthians 6:12, Galatians 3:11-25)?
What is the "liberty" to which Paul and James refer (Galatians 2:4, Galatians 5:1, James 2:12)? If Christians are still in bondage to a law of works, and the sting of eternal death still remains in some sins, then how can a Christian have "liberty", and how can "all things be lawful" to him (1 Corinthians 6:12)? Don't Paul's and James' comments in these passages require that the Christian be free from all bondage of the law, not just some?
If some "really bad" sins cause the loss of salvation, while other sins don't, as critics of eternal security tend to believe, then why do Paul and James say that a person would have to maintain a law of works perfectly in order to be saved by it, and that any violation of any aspect of that law makes a person guilty of violating the entire law (Galatians 3:10, James 2:8-10)?
If perfection is the standard that must be met in order to be righteous before God, as we know it is (Matthew 5:48), then how can anybody hope to attain to that standard through their own behavior (Romans 3:23)? If Christ's perfect righteousness is imputed to us through faith (Romans 3:21-22, 4:5-6, 2 Corinthians 5:21, Philippians 3:9), then why would we need our own imperfect righteousness to be added to His perfect righteousness in order to have eternal life?
If assuring believers of their future in Heaven is wrong, because it encourages them to sin, as critics of eternal security suggest, then why did Jesus and the apostles repeatedly assure believers of their future in Heaven (Matthew 26:29, Luke 23:39-43, John 11:25, Romans 5:9, 1 Corinthians 1:8, Philippians 3:20-21, 1 Peter 1:3-5, 5:4, 1 John 5:13, 2 John 2-3)? Aren't there motivations for keeping our faith, and for not sinning, aside from loss of salvation (Proverbs 22:5, John 14:23-24, Acts 17:31, Romans 5:5, 1 Corinthians 3:11-15, 2 Corinthians 5:14-17)?
If passages like 1 Corinthians 6:9-10 and Galatians 5:19-21 are lists of sins that cause the loss of salvation, as many critics of eternal security claim, then why do we see examples in scripture of people committing those sins, yet remaining saved (1 Corinthians 3:1-3, 11:17-32)? Don't the examples of people committing these sins, yet remaining saved, necessitate that we acknowledge that passages like 1 Corinthians 6 and Galatians 5 are not about how Christians can lose salvation? Instead, aren't they telling believers not to behave like the unregenerate, who prove that they won't inherit eternal life by continually living in sin (1 Corinthians 6:11-12)? In other words, aren't the unregenerate the ones who will not inherit eternal life, as opposed to believers who sometimes commit one of these sins not inheriting eternal life?
Doesn't the man in 1 Corinthians 3:11-15, whose works are entirely bad, yet he's saved, prove that what's at stake as far as the Christian's behavior is concerned is rewards in Heaven, not entrance to Heaven?
When passages like Ephesians 1:7 and Colossians 2:13-14 place no limits on which sins are forgiven, and tell us instead that Christ's sacrifice covered all sins, on what basis can the critic of eternal security maintain that those who have trusted Christ are actually only forgiven of past sins and some future sins that "aren't real bad", while the "really bad" future sins remain uncovered?
If Jesus is the Intercessor for and Advocate of the believer only when the believer commits sins that "aren't real bad", as the critic of eternal security must maintain, then why do Hebrews 7:25 and 1 John 2:1 suggest no such limits? Why do these passages suggest instead that Christ is forever the Intercessor for and Advocate of the believer, no matter what sin has been committed?
If salvation could be lost, it couldn't be regained (Hebrews 6:4-6). How, then, were people like David and Peter saved after committing sins such as adultery and denying Christ? If such sins aren't bad enough to cause the loss of salvation, what would be?
Why does the book of the Bible that most often refers to salvation as a gift (Romans 3:24, 5:15, 5:16, 6:23, etc.) also tell us that the gifts of God are irrevocable (Romans 11:29)?
(NOTE: In another article at this web site, I respond to passages of scripture often cited in opposition to eternal security: http://members.aol.com/jasonte2/eternal.htm.)
"God doth continue to forgive the sins of those that are justified, and although they can never fall from the state of justification, yet they may, by their sins, fall under God's fatherly displeasure; and in that condition they have not usually the light of his countenance restored unto them, until they humble themselves, confess their sins, beg pardon, and renew their faith and repentance." - 1689 Baptist Confession
"For not knowing about God's righteousness, and seeking to establish their own, they did not subject themselves to the righteousness of God. For Christ is the end of the law for righteousness to everyone who believes....You foolish Galatians...Are you so foolish? Having begun by the Spirit [faith], are you now being perfected by the flesh [works]?" - Romans 10:3-4, Galatians 3:1, 3:3
Not what these hands have done can save this
Not what this toiling flesh has borne can make my spirit whole.
Not what I feel or do can give me peace with God;
Not all my prayers and sighs and tears can bear my awful load.
Thy work alone, O Christ, can ease this weight of sin;
Thy blood alone, O Lamb of God, can give me peace within.
Thy love to me, O God - not my poor love to Thee -
Can rid me of this dark unrest and set my spirit free.
Thy grace alone, O God, to me can pardon speak;
Thy pow'r alone, O Son of God, can this sore bondage break.
I bless the Christ of God, I rest on love divine;
And with unfalt'ring lip and heart I call this Savior mine!
(Horatius Bonar, Not What These Hands Have Done)