Matt Chaylock: If science could predict the next thing that happened every time just by looking at your brain, would you say that there's some external source that's also influencing it? "I don't think that's ever possible. Well, it's not possible to do the actual science of it, but certainly it's more of a mental experiment" He says if free will exists, it's probably external or something mysterious to the body, but it would have to be essentially you because otherwise it would be an external force affecting you.