One of the trickier aspects of Christian life is the question of how to approach more difficult passages. Not all Scripture is plain as day, and we often find ourselves asking "what does it mean when it says..."? Thankfully, there are many ways to overcome these difficulties, either alone or in a group. For example, Perspicuity, i.e. we interpret the unclear in light of the clear. To understand Jesus' parables, which are naturally (and intentionally) unclear, we look at the explanations of the parables Jesus gives to His disciples.
One of many difficulties that arise from Scripture is the balance of man's responsibility and God's sovereignty in salvation. Scripture, first of all, tells us that there is a balance. It makes it abundantly clear that man has free will. We are 100% responsible for our own sin, and 100% responsible for how we respond to the Gospel. Scripture tells us that God cannot tempt us to sin (James 1:13), that He cannot lie (Titus 1:2), that He gives us a way out of temptation (1 Corinthians 10:13) etc. Meanwhile, the God who cannot lie tells us that there are possible alternate realities (e.g. Jeremiah 26:3), that He can be grieved by our actions as if somehow they are contrary to His will (e.g. Genesis 6:6), that we can reject His will (e.g. Luke 7:30), and that He commands repentance from everyone (Acts 17:30).
Nevertheless, Scripture also strongly indicates that God is responsible for choosing who He will save. We constantly see examples of God hardening hearts (e.g. Exodus 4:21), giving people over to strong delusions (2 Thessalonians 2:11), and sometimes even sending lying spirits into the mouths of false prophets (1 Kings 22:23). We see that God's counsel stands forever (Psalm 33:11), and even strong evidence that resisting His will is, in the ultimate sense, impossible (Romans 9:19).
Naturally following from the question of free will and the sovereignty of God is the extent of the atonement. Scripture once again clearly tells us that not only is salvation offered to all mankind (e.g. John 3:16), but that God is willing that all men would come to it (e.g. 1 Timothy 2:4). But at the same time, we know that not everyone will come to salvation, and indeed a good portion of humanity will reject it (e.g. Matthew 7:13-14).
Even in this short summary, written by this sloppy author, we see the difficulty in interpreting the Scriptures on this issue. It seems, from my personal studies, that there are 3 main competing views: Calvinism, Arminianism, and Molinism. I have not studied the latter two anywhere near enough to judge the entire philosophies, but Calvinism is something I have spent a considerable amount of time on. Unfortunately, it is a great source of division in the Church. Calvinists often tend to see themselves as superior Christians, looking down on others as uneducated, whereas non-Calvinists all too often overreact in the opposite direction, not only classifying Calvinists as utter heretics, but being so afraid of Calvinism that they even demonise any preacher who simply addresses Romans 9, almost as if they want it expunged from Scripture.
As a Christian, I of course cannot endorse the latter extreme. Romans 9 is Scripture, divinely revealed to the legitimate Apostle Paul, who was hand selected by none other than Jesus Christ to work for His Gospel. Because it is Scripture, it is important not only to keep it in Scripture, but also to study it, even if it is hard, and even if it leads us to conclusions we don't like. As Paul wrote in His letter to Timothy, "All scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness: That the man of God may be perfect, thoroughly furnished unto all good works." (2 Timothy 3:16-17, emphasis mine).
But just as I cannot side with those who treat Romans 9 as if it came from the Qur'an, I also cannot endorse the Calvinist interpretation of it, nor can I take a Calvinist seriously when they insist that those who do not take their interpretation is either uneducated, or unfaithful to God. I can, however, see why one might take the Calvinist interpretation. Romans 9 really does say God loved Jacob and hated Esau, it really does say He will have mercy on whom He wills and hardens whom He wills, and it really does show that God has every right to prepare some as vessels of wrath. For this reason, I cannot class Calvinists as heretics, simply because I can see how Calvinism can be gleaned from Scripture.
I cannot, however, figure out how Calvinism can be sustained from Scripture. As strange as it seems, Romans 9 is not the only chapter in Romans, Romans is not the only book of the New Testament, and the New Testament is only a small portion of the entire Bible. When all relevant Scriptures are taken together, Calvinism becomes completely unsustainable, so much so that there are actually divisions among Calvinists. On the extreme end, you have 5 point Calvinists, some of whom even attempt to follow their worldview through to its natural conclusion. But you also have 4 point Calvinists, with Limited Atonement being the most commonly rejected point. In a sense, you could technically argue I am a one point Calvinist, because I wholeheartedly affirm the Perseverance of the Saints.
Beyond Perseverance of the Saints, every point of Calvinism is critically flawed in some way, not because they find no Scriptural support, but because they find Scriptural difficulties. Total Depravity conflicts with multiple passages which not only tell us mankind has free will, but even present, from God's perspective, that there are alternate possible realities in which those who, historically, did not repent, could have done so. Unconditional Election conflicts with God's explicit statement that whom He foreknew, He predestined, showing us that God's choice of whom He would predestine is based, at least in part, on His knowledge of possible futures. Limited Atonement is firmly contradicted by multiple statements about God's unconditional love for the world, His displeasure in the death of the wicked, His will that all should repent, His lack of will that any should perish, and His command to pray for, and preach to, everyone etc. Irresistible grace is contradicted by those who are explicitly said to have resisted His grace, as well as being the logical conclusion from the fact that grace is offered to all, yet not received by all.
Calvinists, as you can see, have a lot of difficulties to address, but in my experience, they very rarely attempt to address them. When they do, they often make up brand new, unjustified interpretations of the problematic verses, and sometimes even add to the Scriptures. Their arguments promoting and defending Calvinism are almost invariably as incoherent as Calvinism itself.
But I say almost invariably because there is one element of Calvinism that is, at least in my eyes, nigh unassailable. When defending the aforementioned Perseverance of the Saints, Calvinists need not twist, add to, or take from the Scriptures as they tend to do when defending the other 4 points. Scripture does very firmly, even almost explicitly, tell us that we cannot lose salvation, nor will those who are truly saved ever fall away from the faith (though wavering is a possibility). These are easy things to argue for, and very difficult things to argue against, and so we naturally see a change in Calvinist strategies when defending it.
In the end, I must conclude that Calvinism is a "beginner's theology". It is easy to see how a new or inexperienced believer might find Calvinism convincing. However, further study should cause serious doubt, as Calvinism becomes increasingly unsustainable the more we read. When all of Scripture is taken together, only Perseverance of the Saints stands firm. The other 4 points are found lacking to one degree or another.