If you think about our existence in terms of a "universe" meaning that there is only one version of our timeline, then predestination makes sense. If you think about existence in terms of an infinite number of "multiverse's" then you realize that we are just in the timeline where things like Joan of Arc happened, however unlikely. You can then reconcile free will - you have free will in this timeline and the choices you make help determine outcomes. You cannot know the outcomes since there are so many variables, but you can choose to live a life of positivity which typically makes your life a better one.
In Joan's case, she wasn't using her free will.
Instead, she followed the call from God.
It's unexplainable. Literally, her entire existence still can't be explained.
Yet it happened.
I don't believe in multiverse or any other science theory that has no evidence for it.
It's like me saying in another universe, I'm the greatest gambler that ever existed who never lost a bet.
Prove it.
Until then, it's just junk.
The fact that predestination cannot be disproven alarms me.
Because the question then becomes is this really is what is supposed to happen with no way to decide for ourselves?
That's fukkin mind boggling.