" What is it all for? What is the purpose of this activity? And why is it so profitable? Common sense suggests that if a closed circle of people continuously exchange bits of paper with each other, the total value of these bits of paper will not change much, if at all. If some members of that closed circle make extraordinary profits, these profits can only be made at the expense of other members of the same circle. Common sense suggests that this activity leaves the value of the traded assets little changed, and cannot, taken as a whole, make money. What, exactly, is wrong with this common-sense perspective? "

― , Other People's Money: The Real Business of Finance