That's a thoughtful objection, and it's worth answering carefully, because it actually points to the best part of the doctrine.
First, the deceitful heart isn't a Calvinist idea. It's Jeremiah's: "The heart is deceitful above all things, and desperately sick; who can understand it?" (Jeremiah 17:9). If a deceitful heart makes assurance impossible, the objection refutes Jeremiah before it touches Calvin. And it applies to every Christian. Jesus warned that many will say "Lord, Lord" and hear "I never knew you" (Matthew 7:22-23). Every view has to account for people who are sure they're saved and aren't.
Second, read the next verse. "I the LORD search the heart and test the mind" (17:10). Jeremiah's answer to the deceitful heart is not "trust your heart harder." It's "God sees what you can't." That's exactly what I believe. My assurance doesn't come from looking inward and trusting what I find. It comes from looking outward to God's promises: "Whoever comes to me I will never cast out" (John 6:37). "I write these things to you who believe in the name of the Son of God that you may know that you have eternal life" (1 John 5:13). And from his witness, not mine: "The Spirit himself bears witness with our spirit that we are children of God" (Romans 8:16).
Third, total depravity describes the heart before God changes it, not after. "I will give you a new heart, and a new spirit I will put within you" (Ezekiel 36:26). The whole point is that God doesn't leave us with the deceitful heart. He replaces it. And he gives us what we couldn't produce: "he has given us understanding, so that we may know him who is true" (1 John 5:20). Know. Not guess.
So the doctrine doesn't refute itself. It just refuses to put my confidence in me. A deceitful heart is exactly why I need a faithful God. "Search me, O God, and know my heart!" (Psalm 139:23). That prayer only makes sense if the heart can't be trusted and God can.
Ha, deal. I'll gladly keep both sides of 5:15: "much more have the grace of God and the free gift by the grace of that one man Jesus Christ abounded for many." Grace always outruns the fall.
And thank you for the correction on method. You're right, and I'll take it. David's son and the Egyptian firstborn are temporal judgments in specific prophetic moments, and they can't carry the weight of a universal doctrine. At most they illustrate that one person's sin can bring death on others. The doctrine itself has to stand on Romans 5:12-21, Ephesians 2:1-3, and Psalm 51:5, and I should lead with those. Fair hit.
It also sounds like we're closer than this thread looks. You affirm total depravity through Adam, Adam's federal headship, and that no fallen person comes to God unless God enables faith first. That's the historic Wesleyan position, and it's a long way from the people who deny that grace has to come first at all. Our real difference is narrower: whether the grace that enables faith can be finally resisted, or whether it always brings the person home. We both believe adults are accountable moral agents who must hear, repent, and believe. We differ on why one does and another doesn't.
On infants, I take your distinction. They aren't accountable agents the way adults are, and I agree God's mercy reaches them without the response he requires of us. I'd only say that the way God saves them, by his grace alone with nothing contributed on their side, is the way I believe he saves the rest of us too, even though we do truly believe. But I hear you, and I respect how carefully you've thought it through.
This has been one of the best conversations I've had on here. Thank you, brother.
I agree with more of that than you might expect. God does not believe on anyone's behalf. The person believes, with his own heart, and confesses with his own mouth. Faith is a real human act, and Romans 10 makes that unmistakable. And God doesn't override anyone's desires to make them believe. What he does is change the desires. "I will give you a new heart and put a new spirit in you; I will remove from you your heart of stone and give you a heart of flesh. And I will put my Spirit in you and move you to follow my decrees" (Ezekiel 36:26-27). A new heart believes freely, because now it wants to.
So Romans 10 tells us what must happen: a person must believe and call. And it tells us how: "faith comes from hearing the message, and the message is heard through the word about Christ" (10:17). We agree on both, which is why I preach to everyone. What Romans 10 doesn't tell us is why one hearer believes and another doesn't, since both heard the same message (10:16, 18).
But Paul does answer that, and he hasn't changed subjects. Romans 9 through 11 is one argument. Look how chapter 10 ends. Paul quotes Isaiah: "I was found by those who did not seek me; I revealed myself to those who did not ask for me" (10:20). The Gentiles who believed weren't seeking God. God revealed himself to them. Then he turns to Israel: "All day long I have held out my hands to a disobedient and obstinate people" (10:21). The same message went to both. One group was found without seeking; the other refused.
And then Paul explains the difference in the very next chapter: "So too, at the present time there is a remnant chosen by grace. And if by grace, then it cannot be based on works... What the people of Israel sought so earnestly they did not obtain. The elect among them did, but the others were hardened" (11:5-7). That's the same argument as 9:16: "It does not, therefore, depend on human desire or effort, but on God's mercy."
Lydia shows both halves in one sentence. She heard Paul preach, and she believed and was baptized. Every bit of Romans 10 happened in her. And Luke tells us why: "The Lord opened her heart to respond to Paul's message" (Acts 16:14). She responded. God opened. Both are true, and the second explains the first.
So the question I'd ask from your own chapter: in Romans 10:20, the ones who found God "did not seek" him. What made the difference for them?
I agree with your clarification, and I think my last reply landed in the same place: David's son wasn't guilty of David's sin, and his death was the consequence of it, not a punishment of the child. We're on the same page there.
Your question about infants is a beautiful one, and I lean the same way you do. Scripture gives real hope. David, after his son died: "I shall go to him, but he will not return to me" (2 Samuel 12:23). Jesus: "Let the children come to me, and do not hinder them, for to such belongs the kingdom of God" (Luke 18:16). God spoke of Israel's "little ones... who today have no knowledge of good or evil, they shall go in there" (Deuteronomy 1:39). John the Baptist was "filled with the Holy Spirit, even from his mother's womb" (Luke 1:15). Many in my own tradition, Spurgeon among them, believed that every child who dies in infancy is saved, and I share that hope.
But here is the part I'd ask you to notice, because I think it helps my side more than it hurts it.
First, you said Christ's atonement must be applied to infants. I agree. But an atonement only covers guilt. If infants carried no condemnation from Adam, they wouldn't need Christ's sacrifice at all; they would simply be innocent and go to heaven on their own merit. The fact that we both reach for the cross to explain their salvation means we both believe they're under Adam's condemnation and need rescue. That's Romans 5:18. "In Adam all die" (1 Corinthians 15:22), and infants die.
Second, how is an infant saved? Not by deciding, not by understanding, not by choosing. Only by God acting on them by his own grace, without any contribution from them at all. That's exactly what I believe happens to every one of us. An infant in heaven is the clearest picture there is of salvation that is "not a result of works, so that no one may boast" (Ephesians 2:9), and not of "the will of man, but of God" (John 1:13). If God can save a child who can't believe, by giving life through the Spirit, then salvation was never ultimately resting on our ability to choose. It was resting on him.
On Romans 5:15, I'd only add that Paul says the grace abounded "for many," and two verses later he describes them as "those who receive the abundance of grace and the free gift of righteousness" (5:17). Faith is how adults receive it. For infants, God gives what they can't do.
And amen that his glory is his compassion. "The LORD, the LORD, a God merciful and gracious, slow to anger, and abounding in steadfast love" (Exodus 34:6). The same verse goes on to say he "will by no means clear the guilty" (34:7). The cross is where both are true at once.
So I'm still curious about the question from before, because I think your answer to the infant question already answers it: if infants need Christ's atonement, aren't you keeping both halves of Romans 5:18?
Fair challenge, and you've caught a word I should tighten. Neither case is penal substitution, and I didn't mean to claim it; the Egyptian firstborn did not bear the Egyptians' sins the way Christ bore ours, and "punish" is my word for David's son, not the text's. So let me say exactly what the texts say, because the tightened version is still the point.
David: "The LORD also has put away your sin; you shall not die. Nevertheless, because by this deed you have utterly scorned the LORD, the child who is born to you shall die" (2 Samuel 12:13-14). Both halves in one breath: the guilt is put away, and the child dies "because by this deed." How can both be true? Because forgiveness removes guilt before God, not every consequence in time. "The sword shall never depart from your house" (12:10) was spoken to a forgiven man. The child's death was David's chastisement, not the child's: the loss was David's, the shame was David's, and David expected to see the child again (12:23). "The Lord disciplines the one he loves" (Hebrews 12:6) is forgiveness and consequence in one verse. So no, the child was not punished for his own guilt. He died because of another man's sin, by God's own word. That is all I needed the example to show.
Egypt: the intent is not open to interpretation; God states it before the plagues begin. "Israel is my firstborn son... Let my son go that he may serve me. If you refuse to let him go, behold, I will kill your firstborn son" (Exodus 4:22-23). The firstborn died for Pharaoh's refusal, down to "the firstborn of the captive who was in the dungeon" (12:29), who refused nothing. Not substitution. Judgment on a nation that landed on people who did not do the deed.
And it isn't two cases. God sent a three-year famine "for Saul and for his house" and accepted the execution of seven of Saul's sons for Saul's sin, years after Saul was dead (2 Samuel 21:1-14). Achan's sons and daughters were stoned with him (Joshua 7:24-25). Korah's "little ones" went down with the households (Numbers 16:27-33). "Our fathers sinned, and are no more; and we bear their iniquities" (Lamentations 5:7). And Jesus: "on you may come all the righteous blood shed on earth, from the blood of righteous Abel... all these things will come upon this generation" (Matthew 23:35-36). Ezekiel 18 is true, and it is about God's courtroom with a repentant generation: the son is not sentenced for the father's crime. It was never a denial that one man's sin brings death on people who did not commit it. Scripture is full of that, and it tells us why: "sin came into the world through one man, and death through sin, and so death spread to all men" (Romans 5:12). Every infant who dies, David's included, is that verse happening (5:14).
Which is where the whole thing lands. "As one trespass led to condemnation for all men, so one act of righteousness leads to justification and life for all men" (Romans 5:18). Paul builds the second half on the first. If no one can be condemned in another, no one can be justified in another, and the cross goes out with Adam. So my question is friendly, but real: which half of Romans 5:18 do you keep?
Fair challenge on being willing to be wrong. I've conceded points in this very thread: Isaiah 45:7 is mainly about judgment, teleios means complete, and Joshua's "you are not able" is partly a warning. I'm happy to be corrected by the text. So let's stay there.
Does God decree all that comes to pass? Scripture says he "works all things according to the counsel of his will" (Ephesians 1:11). And it says the clearest case of it at the cross, in the same breath as human guilt: Jesus was "delivered up according to the definite plan and foreknowledge of God," and "you crucified and killed" him (Acts 2:23). The rulers gathered "to do whatever your hand and your plan had predestined to take place" (4:28). Planned by God, and freely, guiltily done by men. If that is a contradiction, it's Luke's, not mine.
And the call stays genuine, because the only thing keeping anyone from Christ is his own unwillingness. "How often would I have gathered your children together... and you were not willing!" (Matthew 23:37). No one who wants Christ is turned away (John 6:37).
On history: holding God's decree and real human choice together didn't start at the Reformation. Joseph said it in Genesis 50:20: "You meant evil against me, but God meant it for good." Augustine taught it. Aquinas taught that God moves free creatures in a way that keeps them free, causing necessary things necessarily and free things freely. The word "compatibilism" is modern. The idea is as old as Joseph.
On "righteous outside Israel": Melchizedek, Job, Rahab, Cornelius, yes. And in every case Scripture credits God. Melchizedek was priest of "God Most High" (Genesis 14:18). Rahab said "the LORD your God, he is God" because of what God had done (Joshua 2:11). Of Cornelius, the church concluded: "to the Gentiles also God has granted repentance that leads to life" (Acts 11:18).
And monergism isn't tyranny. A tyrant forces unwilling people. God makes people willing: "Your people will offer themselves freely in the day of your power" (Psalm 110:3). That's the basis of the relationship, not the end of it: "We love because he first loved us" (1 John 4:19). Every real relationship with God starts with his move toward us, not ours toward him.
Honest answer: not the way you've described it. Calvin's own wording on this was sometimes sharper than mine, so let me tell you what I believe and show you where it is.
God doesn't prevent anyone from coming to Christ. No one has ever wanted Christ and been turned away. "Whoever comes to me I will never cast out" (John 6:37). "Let the one who desires take the water of life without price" (Revelation 22:17). The door is open to everyone.
What keeps people away is their own will. "You refuse to come to me that you may have life" (John 5:40). "People loved the darkness rather than the light because their works were evil" (John 3:19). "How often would I have gathered your children together... and you were not willing!" (Matthew 23:37). God doesn't have to push anyone away. Left to ourselves, every one of us walks away on our own (Romans 3:11-12).
So election isn't God stopping some. It's God rescuing some who would never have come. "I will have mercy on whom I have mercy... So then it depends not on human will or exertion, but on God, who has mercy" (Romans 9:15-16). Notice how carefully Paul words it a few verses later. The saved are "vessels of mercy, which he has prepared beforehand for glory." The lost are "vessels of wrath prepared for destruction" (9:22-23). For the saved, Paul names God as the one who prepared them. For the lost, he doesn't. Mercy is God's work. Ruin is ours.
And no one is condemned for a decree. They're condemned for sin. "The wages of sin is death" (Romans 6:23). "Whoever does not believe is condemned already" (John 3:18). The confession I hold says God passes by the rest and ordains them to wrath "for their sin" (Westminster 3.7). Not for anything but their sin.
Yes, God chose before creation; Paul says so: "he chose us in him before the foundation of the world" (Ephesians 1:4). But your view has God knowing before creation exactly who would be lost, and creating them anyway. Neither of us escapes that God knew. The difference is that I believe the ones he saves owe him everything, including their coming.
Thanks for this, I appreciate the tone. Let me take your points together, and start with the most important one, because I think we've been talking past each other.
I don't believe God makes it impossible for anyone to come to him. He never turns away anyone who wants him: "Whoever comes to me I will never cast out" (John 6:37). The problem is that no one wants to come on his own. "You refuse to come to me that you may have life" (John 5:40). "People loved the darkness rather than the light" (John 3:19).
Yes, Scripture says God hardens hearts (Exodus 9:12; Romans 9:18). But when he does, he isn't taking a heart that wanted him and turning it away. He is giving sinners over to what they already love. Pharaoh hardened his own heart (Exodus 8:15, 32), and God confirmed him in it. "God gave them up in the lusts of their hearts" (Romans 1:24). "They refused to love the truth and so be saved. Therefore God sends them a strong delusion" (2 Thessalonians 2:10-11). Hardening is judgment: God leaving people to their own desires.
So the call is completely sincere. Jesus wept over Jerusalem: "How often would I have gathered your children together... and you were not willing!" (Matthew 23:37). A tyrant forbids what people want. God invites, and people don't want him. What God does for his own is give a new heart that does want him (Ezekiel 36:26). He doesn't owe that to anyone. That's grace.
On Deuteronomy 30: you're right about the order. Verses 1-3 speak of Israel returning, and verse 6 follows. But look at what the circumcision produces: "so that you will love the LORD your God with all your heart." The love comes from the new heart. And the chapter before tells us why they needed it: "to this day the LORD has not given you a heart to understand" (29:4). The prophets pick up the same promise with no conditions: "I will put my law within them, and I will write it on their hearts" (Jeremiah 31:33). Paul calls it "circumcision of the heart, by the Spirit" (Romans 2:29), "made without hands" (Colossians 2:11).
The disciples: agreed, they said yes. The question is why. Jesus answered it: "You did not choose me, but I chose you" (John 15:16). Of Peter's confession: "flesh and blood has not revealed this to you, but my Father" (Matthew 16:17). And right after the rich young man walked away: "With man this is impossible, but with God all things are possible" (19:26).
Joshua 24: I kept reading. The people insisted, "we will serve the LORD" (24:21), and I'll grant that Joshua's "you are not able" was partly a warning to test them. But the next generation "did what was evil" (Judges 2:10-11). Joshua was right. Their confident yes didn't last, because the problem was the heart.
The call goes out to everyone, sincerely. The yes that lasts is the one God puts in the heart.
That's the Westminster Confession, chapter 3, from 1646. It sounds strange to modern ears, but every line of it was lifted from Scripture. Here are the verses it summarizes, in the KJV you use.
"The counsel of his own will": Paul's exact words. "Being predestinated according to the purpose of him who worketh all things after the counsel of his own will" (Ephesians 1:11).
"From all eternity... unchangeably": "Declaring the end from the beginning... My counsel shall stand, and I will do all my pleasure" (Isaiah 46:10).
"Whatsoever comes to pass," even sinful acts: "For to do whatsoever thy hand and thy counsel determined before to be done" (Acts 4:28), said of Herod and Pilate.
"Neither the author of sin": "God cannot be tempted with evil, neither tempteth he any man" (James 1:13).
"Nor is violence offered to the will": "Ye thought evil against me; but God meant it unto good" (Genesis 50:20). Joseph's brothers chose freely, and God's purpose stood.
The confession isn't adding to the Bible. It's holding five verses together that a lot of people would rather keep apart. Which of the five would you take out?
Thanks for owning the reference; easy mistake. And you're right about what Calvin says there. He writes that some who are never truly God's children can taste something of his goodness without the Spirit of adoption, and that this leaves them without excuse. I won't pretend he didn't.
But before calling that deception, look at what Scripture says in plainer words than Calvin used. Hebrews describes people who "have tasted the heavenly gift, and have shared in the Holy Spirit, and have tasted the goodness of the word of God" and then fall away (Hebrews 6:4-6). Shared in the Holy Spirit. Jesus says the rocky soil "believe for a while" (Luke 8:13). And Paul goes further than Calvin ever did: "because they refused to love the truth and so be saved... God sends them a strong delusion, so that they may believe what is false" (2 Thessalonians 2:10-11). God sends it.
Notice the order in that verse, because Calvin follows it. The refusal is theirs: "they refused to love the truth." The judgment is God's response to it. No one in Scripture is fooled against his will. People who want a faith that costs them nothing are given what they want. That isn't God deceiving the sincere. It's God judging the insincere, and it's in the Bible whether Calvin ever wrote a word or not.
So if that makes Calvin's God a deceiver, it makes Paul's God one too. I don't believe either. "God, who never lies" (Titus 1:2). It's the same God, and he's the one who promises: "Whoever comes to me I will never cast out" (John 6:37).
@Super_Dan_Dan@NathanBozeman2 Unfortunately I find that very view what to engage on actual scriptural arguments. Too many straw man arguments and mischaracterizations .
I read the section you cited. Book 1, chapter 16, section 9 is about providence and chance: a merchant who wanders from his companions in a forest and is killed by robbers, and how events that look random to us are still under God's hand. It says nothing about false faith or false grace. I think the passage you mean is Book 3, chapter 2, section 11, where Calvin discusses what he calls "temporary faith."
And you're right that he teaches it there: some who never truly belonged to God can feel something close to what believers feel, and later fall away. But Calvin didn't invent that. Jesus did. The rocky soil are "those who, when they hear the word, receive it with joy. But these have no root; they believe for a while, and in time of testing fall away" (Luke 8:13). Believe for a while. Hebrews describes people who "have tasted the heavenly gift, and have shared in the Holy Spirit," and then "have fallen away" (Hebrews 6:4-6). Simon the magician "believed" and was baptized, and Peter told him, "your heart is not right before God" (Acts 8:13, 21). If describing that makes God a deceiver, the charge lands on Jesus' parable before it lands on Calvin.
God deceives no one. "God, who never lies" (Titus 1:2). Scripture puts the deception where it belongs: "be doers of the word, and not hearers only, deceiving yourselves" (James 1:22).
And the point of Calvin's teaching was the opposite of what you're describing. He wasn't trying to make believers doubt. He was pointing them away from their feelings and toward Christ. Later in the same book he says that Christ is the mirror in which we may contemplate our election without deception (3.24.5). Assurance doesn't come from examining how strong your experience feels. It comes from looking at Christ and his promise: "Whoever comes to me I will never cast out" (John 6:37).
Fair point on the word. Teleios in Matthew 5:48 means complete or whole, and the context is love: loving your enemies the way the Father does, sending rain on the just and the unjust (5:43-47). I'll gladly read it that way.
But the point still stands. Who loves his enemies completely, the way the Father does? "We all stumble in many ways" (James 3:2). "If we say we have no sin, we deceive ourselves" (1 John 1:8).
And Jesus uses the same word again with the rich young man: "If you would be perfect [teleios], go, sell what you possess" (Matthew 19:21). The man walked away sad. The disciples asked, "Who then can be saved?" And Jesus answered, "With man this is impossible, but with God all things are possible" (19:25-26). Jesus himself tied the command to man's inability and God's power.
My case doesn't rest on one word anyway. "Circumcise your heart" (Deuteronomy 10:16), then "the LORD your God will circumcise your heart" (30:6). "Make yourselves a new heart" (Ezekiel 18:31), then "I will give you a new heart" (36:26). "Choose" (Joshua 24:15), then "you are not able" (24:19).
I'd genuinely like to hear how you read those pairs. Let's keep it on the text.
If commanding what we can't do on our own is duplicitous, then the charge falls on Jesus, not me. He's the one who said, "You therefore must be perfect, as your heavenly Father is perfect" (Matthew 5:48). No one in this thread keeps that. "We all stumble in many ways" (James 3:2). "If we say we have no sin, we deceive ourselves" (1 John 1:8).
God's commands have always worked in three ways, what the church has called the three uses of the law:
1. They restrain evil in society. Law curbs sin even in those who don't love God (Romans 13:3-4; 1 Timothy 1:9-10).
2. They show us our sin and drive us to Christ. "Through the law comes knowledge of sin" (Romans 3:20). "The law was our guardian until Christ came" (Galatians 3:24).
3. They guide those who already belong to him. "I delight in the law of God, in my inner being" (Romans 7:22).
None of those three says "the command proves you can do it on your own."
And Scripture puts the command and the inability side by side, over and over:
"Circumcise therefore the foreskin of your heart" (Deuteronomy 10:16). Then: "The LORD your God will circumcise your heart... so that you will love the LORD your God" (30:6).
"Make yourselves a new heart and a new spirit" (Ezekiel 18:31). Then: "I will give you a new heart, and a new spirit I will put within you" (36:26).
"Choose this day whom you will serve" (Joshua 24:15). Four verses later: "You are not able to serve the LORD" (24:19).
Right after the Ten Commandments, God says: "Oh that they had such a heart as this always, to fear me and to keep all my commandments" (Deuteronomy 5:29). He commanded what he knew they lacked the heart for.
"Work out your own salvation... for it is God who works in you, both to will and to work" (Philippians 2:12-13).
"Who then can be saved?" Jesus: "With man this is impossible, but with God all things are possible" (Matthew 19:25-26).
And sometimes the command itself carries the power. "Lazarus, come out" (John 11:43) was spoken to a dead man. "Stretch out your hand" (Mark 3:5) was spoken to a withered one. That isn't duplicity. That's grace.
It also isn't unjust, because the inability is moral, not physical. A man who wastes his paycheck still owes the debt. We still owe God love with all our heart, even though we've turned our hearts away from him. The command tells the truth about what we owe. The gospel tells the truth about who pays it.
Augustine prayed it this way 1,600 years ago: "Give what you command, and command what you will."
You say I ignore the places Scripture says the opposite. Name one, and I'll gladly deal with it.
Amen. He runs. That is the heart of God, and it is what this chapter is for.
Jesus told it because the Pharisees murmured, "This man receiveth sinners, and eateth with them" (Luke 15:2). He answered with three stories and one moral: "joy shall be in heaven over one sinner that repenteth" (15:7). The father who runs and the elder brother who "would not go in" (15:28) are the point.
So I would not use it to settle how a sinner comes home. The chapter pictures that three ways. The sheep is carried: the shepherd goes "after that which is lost, until he find it" and "layeth it on his shoulders" (15:4-5). The coin is searched for: the woman seeks "diligently till she find it" (15:8). The son walks. Jesus is not giving three orders of salvation. He is showing one heart. Press every detail and the story would teach forgiveness with no cross.
Luke names the seeker: "the Son of man is come to seek and to save that which was lost" (19:10). And when Jesus teaches how a man comes to life, he says it plainly: "Except a man be born again, he cannot see the kingdom of God" (John 3:3).
The God who runs in verse 20 is the God who seeks in verses 4 and 8. Come home. He runs.
Having the faculty to trust doesn't mean the heart wants to trust Christ. That's not a new definition. It's the difference between a faculty and its object.
An unfaithful husband has the faculty to love. He loves plenty. He just won't love his wife. No one says "if he can love anyone, he can love her, so his problem must be ability." His problem is his heart.
That's exactly how Scripture describes us. Fallen people worship. They just worship the wrong thing: "they exchanged the truth about God for a lie and worshiped and served the creature rather than the Creator" (Romans 1:25). They love. They just love the wrong thing: "people loved the darkness rather than the light" (John 3:19). The faculty works. The direction is wrong.
And it isn't one text. It's John 3:3, 3:19, 5:40, 6:44, 6:65, 8:43-47, Romans 3:10-11, 8:7-8, 1 Corinthians 2:14, Ephesians 2:1-5, Philippians 1:29, and more. Paul puts the whole thing in one verse: the mind set on the flesh "does not submit to God's law; indeed, it cannot" (Romans 8:7). Cannot, because it is hostile.
That's why we need more than a better argument. We need a new heart. "I will give you a new heart" (Ezekiel 36:26).
Thank you for saying that Calvinists who truly believe in Christ are not lost. That matters, and I receive it gladly. I'd say the same of you: everyone who trusts in Christ alone is my brother, whatever we think about how he got there.
Now the assurance question, because it's a fair one. You're right that some in my tradition have struggled with assurance; the Puritans wrote whole books about it. But the problem you describe isn't unique to Calvinism. It's in the Bible, and it's there for everyone. Jesus: "On that day many will say to me, 'Lord, Lord, did we not prophesy in your name?'... And then will I declare to them, 'I never knew you'" (Matthew 7:22-23). The rocky soil "receives it with joy, yet he has no root in himself, but endures for a while" (13:20-21). John: "They went out from us, but they were not of us" (1 John 2:19). Every Christian, whatever his view, has to reckon with the fact that some who profess faith don't have it.
And God doesn't fool anyone. "God, who never lies" (Titus 1:2). "It is impossible for God to lie" (Hebrews 6:18). False faith comes from a deceitful heart (Jeremiah 17:9), not from God.
So where does my assurance rest? Not on how strong my faith feels, and not on my own decision, because a decision I made I could unmake. It rests on God's promises and God's grip. "Whoever comes to me I will never cast out" (John 6:37). "I write these things to you who believe in the name of the Son of God that you may know that you have eternal life" (1 John 5:13). "The Spirit himself bears witness with our spirit that we are children of God" (Romans 8:16). "He who began a good work in you will bring it to completion" (Philippians 1:6). "No one will snatch them out of my hand" (John 10:28).
That is the sweetest part of sovereign grace for me. If my faith came from God, then the God who gave it will keep it. My assurance doesn't depend on how well I hold on to him. It depends on how well he holds on to me.