Every once in a while I don't mind a dash of Calvinism because they are healthy reminders that there is a real, genuine terrible hell, and that people really do go to an actual hell. Too many moderns do not preach fear of going to hell enough, to be honest. So sometimes I joke that we need some fire and brimstone preaching about hell from Calvinists.
However, there is a very fundamental error in Calvinism (beside the whole Protestant split from Catholicism quarrel) that needs clearing up. Calvin and his followers believe in "predestination," which is the cause of much of the historic antagonism between Calvinism and Catholicism. Catholics assert that there is free will, where people choose whether or not to sin, and thus must bear the consequences of sin. Calvinists believe that all of this is "predetermined" before one is born, and thus one is born to either be saved to heaven or doomed to hell, no matter what that person does.
Predestination is an error and is incorrect. It results from a misunderstanding of God's "all knowing-ness." For those of you new to my blog or new to reading my "understanding God" series, if you follow the label you will be able to read what I have previously written about God's attributes (for lack of a better word), including his knowledge of all that was, all that is, all that will be, and all that could ever be (the answer to every "what if" question), to the minutest level. I discuss how God knows the action, past present and future, of every subatomic particle, no matter how small, every void of space, and all the matter, energy, time and nothingness that ever was, could be (if God had willed it to be), or will be (what he does will). For example, God knows each subatomic particle in one cell of your skin, for example, knowing where each particle came from and where it is going, to the end of time.
Thus God knows the thought of every human being, their intentions, their actions, and also all that they have done and all that they will do. However, there is a great difference between God knowing what one will do throughout life (and thus where one will go after life, when one dies) and predestination. God knows what choices you will make in life, but God still allows you to make those choices, one after the other. If one was genuinely "predestined" to heaven or hell, God would not allow humans to make individual choices about behavior day to day. You would find that you are marching through a script, and that most certainly is not true. So Calvinists believe that a person is going to go to hell, for example, no matter what they do in life, and likewise someone else is destined to heaven. That most assuredly is not true and both God in the Old Testament and Jesus Christ in the New Testament emphasize that one must make continual choices throughout life, to be righteous or to sin. God knows what choices each person will make, but that does not mean that God has made those choices for you.
Each person still has to make individual choices that in sum total are 1) acceptance of the grace of God and 2) are righteous and 3) are genuinely repenting of sin in order to achieve heaven. In other words one has to live life, step by step, decision by decision, and God is not going to make those decisions for you. God knows what you will decide and that is God's "all knowing." However, you still have to live your life and work to make good life affirming decisions, and to shun and regret sin when it does occur.
Think about it with this theoretical. Suppose one felt that he or she was "predestined" for heaven, no matter what he or she did. Would that incline a person to be very mindful of the consequences of their behavior? No, it would not. Likewise a person who thinks they are predestined to hell will not make much of an effort to do what is right. Predestination is such a pernicious and filled with despair attitude that it gave qualms to even some of the most holy of the saints, when they encountered this idea in their youth. What people must remind themselves of is what is in the Bible. From cover to cover, and with plain and loving but stern speech by Jesus Christ himself, the Bible teaches the avoidance of temptation and evil and the choosing of the good. The Bible would not continually teach good choices in life if the fact was that the choices were already made for someone due to "predestination."
So the Calvinists misunderstand the fact that God knows in advance the heart and the deeds of all humans with thus assuming that God has predetermined as in established as a fact where they are going before they are even born. This is simply not true and remember, God created humans in the first place so that they can make choices and be individuals who elect God and love their neighbor. If God wanted robots he would have created really good ones and not have bothered with either humans or angels (who also made their choice whether to serve or to not). God knowing in advance what choices one will make does not mean God requires, forces, or guides one's steps inexorably down that "path" to either heaven or hell. Each human does that all on his or her own, with each step of their life.
Remember too that God would not have given each person guardian angels if the purpose of the angels was just to watch one group march to hell, and the other group to heaven. Angels interact with humans with a continual bias and spirit toward doing the good, doing the best, and resisting temptation. Likewise the Holy Spirit moves constantly among all people, those who are making good choices but especially among those making bad choices, trying to guide them back to the healthy, the good, the loving and the righteous. I hope that you have found this helpful.
And if it seem evil unto you to serve the Lord, choose you this day whom ye will serve, whether the gods which your fathers served that were on the other side of the flood, or the gods of the Amorites in whose land ye dwell: but as for me and my house, we will serve the Lord.