Oh does it I'm glad you know everything.
So do tell me, where does my imagination get it from?
At a fundamental level it's chemical releases caused by pattern matching.
Ideas that feel right match patterns that trigger chemicals that hit the pleasure sensors.
If you want to know how the brain works then there is plenty of information from the scientific community, not so much from the religious community.
Our physical bodies certainly are, but is that all there's to it?
There is no proof either way, most religions do require you to believe there is more to it.
Science isn't as bold as religion in an answer to that question. A scientific answer would be, does there need to be anything more for the system to work? Is what we consider a soul just the configuration of neurons in the brain?
Science can't prove there isn't a soul, isn't a god or that god doesn't communicate directly with a soul. A scientist will only ever offer proof for an alternative explanation. Religion requires you to believe in things with no proof.
There is very little different in a theist and an atheist. An atheist disbelieves in all religions, a theist disbelieves in all but one religion. I don't know what makes someone believe in one religion over others, when none of them offer proof. It seems to me that people fall in love with religion the same way they fall in love with people.