Doctrines of (dis)Grace

According to this source,

The doctrines of grace, also known as the five points of Calvinism, summarize key aspects of Reformed theology regarding salvation. They include Total Depravity (humans are utterly sinful and incapable of saving themselves), Unconditional Election (God chooses whom to save based on His will alone), Limited Atonement (Christ's death specifically secured salvation for the elect), Irresistible Grace (God's grace effectively brings the elect to salvation), and Perseverance of the Saints (those truly saved will persist in faith until the end). Together, these doctrines emphasize God's sovereignty and grace in the salvation process.

Now we need to clarify some things. The term "total inability" is often preferred over "total depravity", since they admit that not everyone is utterly depraved, but rather everyone completely lacks the ability of self-salvation. (Of course, no non-Calvinist believes we save ourselves; accepting the gift of salvation is not saving ourselves.) Grace being "irresistible" means that God forcefully 'regenerates' a person so they will have no choice but to accept the Gospel. Also, Calvinists define "perseverance" as that we can only know if we were 'elect' if we maintain our faith till death; no one can be sure of their salvation while alive. These five points are commonly referred by the acronym TULIP.

The most important point to recognize is that the U, L, I, and P all stand or fall on the T; only if T is true are the other letters even necessary, and if T is not true, none of the rest of them are. So all we really need to focus on is the T: Is it scriptural or not? Are we born sinners, because we inherit a "sin nature" from Adam?

Augustine

The teaching of an inheritable sin nature did not originate in scripture, but came instead from the influential teachings of Augustine who, even after leaving Manichaeism, still held to some of Mani's principles (Augustine and Manichaeism). A quote from the link:

Manichaeism offered Augustine a way to accommodate his conflicts: he could pursue his career, and retain his partner, while purging his sins through his service to the pure Elect; and he could blame those sins on his lower, alien nature, which like the material world had been made by the power of evil, but which his true self would eventually shed. Manichaeism also responded to his need, instilled by his childhood, for the name of Christ, and his initial distaste for the Christian scriptures. He could regard the Bible as a crude and contaminated attempt at the truth, whereas the Manichaean scriptures offered both the name of Christ and what seemed to be a profound understanding of the universe and of human life.

Though Augustine eventually left Manichaeism, he retained its teaching of the sinful nature of mankind. A thorough examination of this belief can be found at St. Augustine's Doctrine of Original Sin. Augustine argued that if it were unjust for God to send babies to hell, then it would also be unjust for God to allow babies to suffer at all. Yet this leads to the conclusion that God should therefore never have created any being that would defy him, because some might otherwise choose to do evil and set consequences in motion that would affect the innocent. So Augustine's teaching creates an impossible dilemma: God could not be just or loving if he gave people free will, yet creating them without free will would make God responsible for sin.

Augustine's dilemma is solved by acknowledging that free will necessarily involves true choice between good and evil, and that people must either enjoy or suffer the consequences of their— and others'— choices. Only people free to choose can offer genuine love and devotion, so God could not create puppets or robots. That is, the love of God (which is his nature) requires the free will of people.

But what of the innocent suffering for the sins of others? Justice is not denied forever; God will eventually compensate everyone accordingly. Since people cannot help that they're born in a wicked world and a body that has physical demands, God offers a genuine choice for everyone to be generously compensated in eternity. That some choose to reject this offer is no fault of God's, and that other choices besides heaven and hell don't exist is no denial of justice or mercy.

Free will is a matter of understanding, consent, and genuine choice, and love cannot be genuine unless it's given freely. Thus the teaching of Original Sin stands in direct opposition to the love and justice of God. Augustine saw it as simply the mirror image of Jesus dying for us all without our request or consent, yet this is a false comparison, since Jesus' death and resurrection do not force anyone to accept him, but simply make the offer possible. Otherwise we would make nonsense of scriptures such as Rom. 5:9-10 and 2 Cor. 5:18-20, which tell us both that we are reconciled and that we must be reconciled. One person cannot force another to reconcile; by definition, reconciliation requires the willing agreement of both parties. The Bible is replete with God's injunctions to choose wisely, which would be rendered a cruel hoax if Original Sin were true.

If you believe you were born a sinner, then you must also believe that you're not responsible for your sin; there is no escaping this conclusion. All of us know that we choose to sin, and we know that we're only held responsible for what we choose to do. To know all of this, yet at the same time cling to what tradition and many (but certainly not all) scholars teach about Original Sin, is to believe in an unscriptural contradiction.

Calvin

Does character matter? One cannot read the New Testament without affirming that it not only matters but is vital (e.g. Gal. 5:22-23). We've seen how the character of Augustine led his theology to excuse his sin, but the character of Calvin was wholly unchristian. According to this source, Calvin got his theology almost completely from Augustine, who insisted that the church had the right to impose its will by force. He carried it out with an iron fist:

[Calvin admirer] Cottret documents the dates of executions and the methods of persecution, torture, and execution. He describes the period of time when Calvin had much authority in Geneva; and when Calvin denounced someone as a heretic (often the denouncement came for criticizing or even just questioning Calvin's teachings) that person was hunted down. Cottret describes the atmosphere during this time:

Fear of sorcery and of heretics entailed their retinue of hasty, indeed barbarous remedies: imprisonment, torture, the stake.

...

It puzzles me immensely why anyone would think that God would use such a man as Calvin to be a great leader of Christianity?

Should we as Christians take even limited parts of our theology instruction from the likes of Calvin and Augustine? "By their fruit you will recognize them", said Jesus in Mat. 7:16. Now let's examine some details stemming from their unscriptural teachings.

Detailed Claims and Rebuttals

Claim: Human spirit literally died when Adam and Eve sinned.

Rebuttal: Not one scripture teaches this, expressed or implied. All references to spiritual death are figurative and indicate separation and captivity. Adam and Eve became mortal when they ate the fruit, then Adam was forbidden to eat the remedy (the fruit of the Tree of Life), and further curses were pronounced on nature, due to his having openly blamed God for his sin (Gen. 3:12, 17-19, 22-24). Neither does any scriptural reference outside of Genesis imply such a concept. And since those who are in Christ have "died to sin" (Rom. 6:2, 7:9, Col. 2:20), literal spiritual death would make this mean that Christians are incapable of sinning, in contradiction of 1 John 1:10.

Claim: Every person ever born was born a sinner, so none of us can avoid sinning.

Rebuttal: Poetic hyperbolic expressions of guilt and remorse aside, no scripture teaches this. What it does teach is that death came into the world because of the first sin (Rom. 5:12), and that though everyone dies, not all sinned the same as Adam (Rom. 5:14). Since Adam and Eve sinned in an environment devoid of suffering and with direct access to God, and since they were not created with any "sin nature", then none of those excuses can explain why they sinned. So there was some other cause, and that cause was free will. That is, we sin because we choose to. And if people can sin in an optimal environment, the likelihood of sinning increases greatly in a hostile environment. We should also note that Rom. 5:12-21 (esp. 15, 18-19) becomes hopelessly incoherent if we try to keep to the literal meanings of "all" and "many"; if all without exception were made sinners, then all without exception were made righteous.

Claim: We sin by choice and are thus responsible and accountable, in spite of the fact that our inherited nature can choose nothing else.

Rebuttal: If we sin because our nature compels us, then we cannot be held responsible for it. A moral choice requires the option to sin or not, rather than simply which sin to commit. And if God gives us this nature, then God is still the cause of our sin, just as a robot can only do what it was programmed to do; the programmer cannot escape responsibility. The teaching that God would create us as sinners, yet punish us for sinning, is an insult to the holiness and justice of God. God is love, and nothing God does can operate in a moral vacuum. God cannot be less just and fair than humans, and even monkeys know when they're not being treated fairly. (Disclaimer: The article's references to evolution are neither relevant nor endorsed by this site.)

Claim: Sin is passed down through males, which is why Jesus could not have a human father.

Rebuttal: First of all, there is no "sin gene", and scripture directly refutes this claim (Ezk. 18:4, 13b, 17b, etc.). And if spiritual death can be inherited, so also can spiritual life, meaning the children of saved parents should be born sinless. It's a special pleading fallacy to believe that only the lost can pass down their spiritual nature, and absurd to argue that dead spirits can reproduce at all. And if it is then argued that the spirits of children come from God, this would make God the author of sin. But rather than throw out God as the creator of souls, we should throw out the idea of inheritable sin.

Secondly, Jesus' earthly mother Mary was a sinner like anyone else (Luke 1:47 "my Savior") and had a human father like anyone else; there is nothing in scripture to make her or her parents sinless. The idea that human flesh is intrinsically evil comes from Gnosticism, not the Bible (see Rom. 8:3, Heb. 2:17), while other references states that Jesus was sinless (2 Cor. 5:21, Heb. 4:15, 1 Peter 2:22, 1 John 3:5). Having eliminated the claim of inherently evil flesh, the only explanation remaining for Jesus having no human father was because he is God (Isaiah 9:6, Mat. 1:23, Heb. 1:3, 8-9), who took on human flesh at a point in time and became the Son as well (Isaiah 9:6, Phil. 2:5-11, Heb. 1:5-6).

Claim: When Adam and Eve sinned, they were no longer made in the image of God, so no one else has been made in God's image since then. We only acquire that nature when we're saved.

Rebuttal: Gen. 9:6 and James 3:9 indicate that all people are still made in God's image.

Conclusion

Much more can be said on this perpetually-debated topic, and I encourage you to read more about Calvinism and Augustine (esp. Augustine's lack of knowledge of Biblical languages). But it's been sufficiently established here that we're not born sinners with an inherited "sin nature"; we simply choose to sin or not. Such choice does not mar the sovereignty of God, who has no fragile ego to defend. He wants most of all for us to return his love, which isn't genuine without the free choice not to love. The "doctrines of grace" know nothing of grace as defined in scripture.