What is "the spirit of this world." referred to by John-Paul II

The Wikipedia article on the "Prayer to Saint Michael" (http://en.wikipedia.org/wiki/Prayer_to_Saint_Michael) says that Pope John-Paul II referred to "the spirit of this world" when recommending the prayer be used by Catholics. Here is the quote from the article: "Although this prayer is no longer recited at the end of Mass, I ask everyone not to forget it and to recite it to obtain help in the battle against the forces of darkness and against **the spirit of this world**." What did JP II mean when he used this expression "spirit of this world"? The Saint Michael prayer mentions "the devil", "Satan", and "evil spirits". Are they all different? Does "spirit of this world" mean "the devil", "Satan", or "evil spirits" ?