what is the "spirit of the world"?

The Scriptures tell us: “We received, not the spirit of the world, but the spirit which is from God.” The "spirit of the world" is the same spirit as that mentioned at Ephesians 2:2, which says: “You at one time walked according to the system of things of this world, according to the ruler of the authority of the air, the spirit that now operates in the sons of disobedience.” This “air” is the world’s spirit, or mental attitude, and it surrounds us like literal air. It is everywhere. It is often manifested in the no-one-is-going-to-tell-me-what-to-do or the fight-for-your-rights attitude of so many people today. They constitute “the sons of disobedience” of Satan’s world soon to be removed.