I'll tell you what I believe. Lizard Dude may or may not agree with me.
An alternative view to free will is determinism, which states that every event, including human cognition, behavior, decision, and action, is causally determined by prior events. At some point, determinism asserts that our "decisions" are not caused by free will, but by chemicals located in the brain. It is purely naturalistic and does not go so far as to claim that the brain/body is separate from the mind.
For example, if I am hungry, I do not eat because I want to. I eat because said chemicals "tell" me to eat. Most Christians, I assume, deny determinism because it suggests that we have no souls.