And do believe that I, this random guy on the internet has a soul
I personally don’t believe that I anyone else has a soul. From my standup I don’t se any reason to believe that our consciousness and our so called “soul” would be any more then something our brain is making up.
You’re right that we need a definition, but that doesn’t mean it has to be based in the natural world. Science could never conclusively prove/disprove the existence of a soul because it’s inadequate in this context.
The only scientific way to do it would be to compare a large group of people who definitely didn’t have a soul with another large group too see if there’s any consistent differences. Given that the experiment itself implies the existence of a soul it all becomes a little circular.