2:2

the system of things of this world: The Greek word here rendered “system of things” basically means “age.” It often denotes the current state of affairs or features that distinguish a certain period of time. The Greek word for “world” (koʹsmos) here refers to the unrighteous human society alienated from God. In this verse, where these two terms are combined, the whole expression could be rendered “the course [or, “customs; ways”] of this world,” referring to the behavior and standards of people alienated from God. Paul makes the point that the Christians in Ephesus had once led, or walked according to, an unrighteous way of life.

the ruler of the authority of the air: Satan the Devil is the “ruler” referred to here. Paul uses the literal air, or atmosphere, to illustrate how the spirit, or dominant attitude, of selfishness and disobedience permeates the world today. Paul uses similar language at 1Co 2:12 in referring to “the spirit of the world.” Just as literal air is everywhere, ready to be breathed in, so “the spirit of the world” is always present. It exerts “authority,” or power, over most of mankind. The power of this dominant mental attitude lies in its appeal to the sinful flesh, its subtlety, its relentlessness and, like air, its pervasiveness. Those who are alienated from God and who pursue a course contrary to God’s will are here called “the sons of disobedience.”

the sons of disobedience: See study note on Ac 4:36.