The idea of souls have been universal in all societies throughout human history. It started when the first person was buried and someone said a few words about the dearly departed. It's the vehicle through which people will enter the happy hunting grounds, heaven, hell, Valhalla, or paradise. It's the hope for something better for "good" people and the curse of something worse for "bad" people.
Even if a person isn't religious he will usually believe in the idea of a soul by saying something like "go to hell".
Even if a person isn't religious he will usually believe in the idea of a soul by saying something like "go to hell".