Q: Is there a word for a person or action where they no longer believe in something? I am not looking for "apostate". Rather, I am looking for the word (verb/noun) which means that someone no longer thinks along those lines as they did before. In short, they gave up their old ideas.

A: 'To recant (on ones position)' might fit what you're looking for.
If it's more religious in context then 'to lose (ones) faith/belief' is a good fit.
