What do we do while deciding if free will exists?

[JuliaL]

I see the argument over free will as very similar to the one over absolute morality being law from a metaphysical lawgiver.

I doubt I would act differently if there

1. was a God who gave moral law and would someday punish infringement but had no sensible, current manifestations or
   
2. was no such God but, in exactly identical fashion to the above, I mistakenly thought there was.
   

Similarly I would not be able to discern between the following

1. I had a free choice to select between various, potential world paths and
   
2. I had no such free choice but thought that I did with no evidence to prove I was in error.
   

If there is no way to currently tell a difference between 2 states, then there is no current difference.