@Johann
Calvinism is remarkably consistent and defined.
“Calvinism is the broadest and deepest Christianity; or, if you will, it is the purest Christianity; or, as I should prefer to qualify it, it is the most consistent and likewise the most harmonious Christianity.” Dr. R.C. Sproul
But what is at the heart of the Calvinistic system? Many people have tried to break it down to one principle or a single concept that governs Calvinism. I personally don't think that's possible. Here is a short list I believe are the most Important.
Predestination. This one trips a lot of people up. Some say predestination is the core of Reformed truth, that assertion can be misleading if You think that everything proceeds from absolute predestination in such a way that what transpires in time matters little. You can lose all sense of reasoning if you get too far into this one. This hyper-Calvinistic view leads to a tendency to move away from biblical revelation into a more rationalistic kind of theology.
The covenant. While the covenantal relationship between God and man is emphasized in Reformed theology, it is not necessarily the controlling concept. All men are indeed either in covenant with God or are covenant-breakers, but Calvin did not structure all doctrines under this important truth. I personally think he missed the mark on this one.
The sovereignty of God. Sovereignty means “rule”; hence, to speak of God’s sovereignty is to refer to God’s rule. God’s sovereignty is His supremacy, His kingship, and His deity. His sovereignty declares Him to be God, the incomprehensible Trinity who is nevertheless knowable insofar as He chooses to reveal Himself to us. His sovereignty is exercised in all of His attributes, declaring Him to be perfect in all respects and possessor of all righteousness and holiness. He is the sovereignty gracious and omnipotent Jehovah, the Most High.
So now we need to the true nitty gritty of Calvinism. As Calvinist I believe that God is the Lord of life and Sovereign of the universe, whose will is the key to history. I believe that He is free and independent of any force outside Himself to accomplish His purposes; that He knows the end from the beginning; that He creates, sustains, governs, and directs all things; and that His marvelous design will be fully and perfectly manifest at the end of the ages. “For of him, and through him, and to him, are all things: to whom be glory for ever” Romans 11:36
“God’s sovereignty is to all other doctrines what the granite formation is to the other strata of the earth. It underlies and sustains them, but it crops out only here and there. So this doctrine should underlie all our preaching, and should be definitely asserted only now and then.” Charles Hodge
God’s sovereignty is the heart of Calvinism one needs to understand that this sovereignty is not arbitrary but is the sovereignty of the God and Father of our Lord Jesus Christ. The sovereign grace and love that went to Calvary has the whole world in its hands. God’s fatherly sovereignty in Christ is the essence of who God is.
