INTRO: Our subject is spiritual warfare. One of the most difficult things about this battle is that we do not see the enemy. Like the wind, we can't see our enemy, but we experience the effects of them. But for a large part of lost mankind, and many Christians, we do not recognize demonic activity. Only when it becomes extreme do we recognize it. But yet our passage says, "We wrestle not with flesh and blood, with principalities, with powers, with the rulers of the darkness of this age, with spiritual wickedness in the heavenlies." There is our entire battle, and we may fail to recognize much of it.
I do wonder sometimes to what extent many of us as Christians bother the devil. How much of a threat are we to him? But on the other hand, anyone who truly belongs to the Lord by salvation is someone Satan wants to steal and bring him into his own domain. So though they may not be the threat that causes great concern for him, yet he is not content to leave them without seeking to bring them back to his fold. So every Christian is in this battle to some extent.
So we are to take up the whole armor of God, number one being truth; number two, living right; number three, stand on the solid foundation of the Gospel; number four, taking up the shield of faith; and now, taking the helmet of salvation. We might think of this armor like this: there are those things fastened to the body and are worn throughout the day. The belt and the breastplate and shoes would be worn all day and were attached to the body. The helmet, shield, and sword would be taken off when resting or eating.