Many people don’t have an accurate understanding of the origins of Calvinism. Many will say that it’s origin is with John Calvin and it’s solely man-made philosophy. This has already been answered in previous posts.
Calvinism as we understand it today, usually summarizes in the acronym T.U.L.I.P. was actually a response to Jacob Arminius and his teaching. Many reformers were concerned over his new readings of passages of Romans. Over time, Reformed churches started to take notice from all over Europe.
Followers of Jacob Arminius published a remonstrance against the Reformed Churches in regards to 5 areas of doctrine. These became known as the 5 Articles of the Remonstrants. The Reformed Churches then met from all over Europe in Dordrecht, The Netherlands in 1618. They countered these 5 articles point-by-point in what’s known as the Canons (or rules) of Dordt.
The 5 Articles of Remonstrants were as follows: Election was conditioned upon foreseen faith and obedience; Universal atonement; Regeneration enables sinners to do good toward salvation; Resistible grace; Believers may fall away.
The Canons of Dordt did not create the T.U.L.I.P acronym. They went into greater detail dealing with these doctrines in depth. A great short history that deals with the order and doctrine that they defended is written by R. Scott Clark from Westminster Seminary in California. I would strongly encourage you to read it in full, it is one of the best, concise handlings of the history of these doctrines.
In summary the Canons of Dordt concluded that The Five Articles of Remonstrants were indeed gross error. Rather affirming our Total Depravity, that our election by God is unconditional, that the atonement is limited in its scope, that those whom the Spirit regenerates cannot resist, and those who the Father elects, the Son atones for, & the Spirit draws, will persevere until the end by the power of God.
I’ll end with a quote from R. Scott Clark:
The Canons of Dordt represent a remarkable consensus of conviction among the Reformed churches on essential doctrines. Indeed, the very Reformation was at stake. If God’s favor is conditioned upon anything in us, then we are lost because we are dead in sin. If the Gospel is reconfigured to include our obedience, then it is no longer the Gospel. If atonement is merely hypothetical, if the elect can fall away, then grace is no longer grace.