plz explain the term "soul of the world" used by paulo coelho in his novel "alchemist"?

Answer 1

I think it is deliberately vague. It means what it means to each reader. "Soul" is difficult to define anyway. Your soul is what makes you alive, and what makes you unique from other people -- your deepest innermost self. I read that phrase as that part of people that is the same all over -- humanity.
The book is a vague, philosophical treatise. Kind of like how fortunetellers are vague in their predictions or visions. If it is too specific, it doesn't apply to everybody, and is, therefore, less powerful.

Answer 2

Soul of the World Exactly is what it says it IS.