My reason for not being a Calvinist is simple; Calvinism wasn't invented by Jesus. The truth is, many of the beliefs that mark Calvinism can not be defended unless certain scriptures are conveniently reinterpreted to mean something other than what they seem to say at face value. A few examples;
John 3:16 For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life.
This scripture seems to indicate that "whoever" believes in Jesus will have eternal life. This doesn't fit well with a Calvinist view of predestination or with its view on the free will of man (or their lack of free will, rather). This verse is a powerful evangelistic proclamation of God's intent towards all mankind, yet I have seen Calvinistic viewpoints try time and time again to water it down and make it mean something else.
That is why we labor and strive, because we have put our hope in the living God, who is the Savior of all people, and especially of those who believe.
"The Savior of all people?" But I thought that his atonement was only for those who were predestined to believe? Don't worry, its just another verse that doesn't line up with Calvinism.
The Lord is not slow in keeping his promise, as some understand slowness. Instead he is patient with you, not wanting anyone to perish, but everyone to come to repentance.
This verse seems to communicate that God doesn't want anyone to perish "but everyone to come to repentance". I don't know how that can square with a belief that God predestines some people to go to hell. It seems that if God was choosing for people whether or not they can believe then his hearts intent would be to make everyone trust in Christ.
Now, I know what you're thinking, "but what those verses really mean is...!" I have no doubt that Calvinism has an answer for each of these verses but my point isn't that Calvinism can't be defended. My point is this; Calvinism needs defending to stand up against me reading a few simple verses out of the Bible.
Why would I want to cling to a belief system that requires my constant defending? I think I am better served to only maintain those beliefs which I feel are apparent and let God increase my understanding of everything that doesn't make sense to me yet. I don't know how predestination works. I don't understand why God hated Esau but he loved Jacob. I don't understand a lot! I feel like some things aren't meant to be understood by our finite and error prone human reasoning.
I feel like many of us put the cart in front of the horse by pushing our beliefs on others instead of letting our viewpoint be stretched and tested continuously by God's word.
But the real cost of switching from "I wonder" to "I know" in areas of disputable doctrine is that we tend to get puffed up by our knowledge. And we know that along with pride comes contention. Hence the endless Facebook debates, Twitter rants and blog posts.
We need to stop dividing ourselves over trivial ideas that have no influence on what really matters; Loving God and loving others.
Do nothing out of selfish ambition or vain conceit. Rather, in humility value others above yourselves - Phillipians 2:3