You would not say, “Oh, he must have hard skin,” or, “He must be slimy.” You would not look at me in exasperation and say, “Well which one is he?! A snail or a turtle?” Why is it then, that we do that to the Bible when the Holy Spirit uses figurative language?
Usually there is only one point to a figure, whether it is as small as a metaphor or as complex as a parable. God can call the church a family, an army, a vineyard, a kingdom, and a bride. There is a point of emphasis for each figure. Most of us get that one, but then do crazy things with the parables, finding and binding points where there are none, or tying ourselves into knots trying to explain why both Jesus and the apostles’ teaching are called “the foundation.” Bible study wouldn’t be nearly as difficult if we used the same common sense with it that we do with everyday language. That’s why the Holy Spirit used common language—so we could understand
Eph 6:16 says faith is a shield. 1 Thes 5:8 says faith is a breastplate. Couldn’t Paul get it right? Yes he could, and yes he did. Faith is either one depending upon the point you are trying to make.
The word for shield in question is used only that one time in the New Testament that I could find. In its etymology, it originally referred to the stone that covered the door of a cave. That immediately brings to mind the stones that covered both Jesus’ and Lazarus’s tomb-caves. The door had to be heavy so a scavenging animal could not dislodge it. It had to completely cover the opening so that after four days, as Martha reminded Jesus, the smell wouldn’t get out.
The word was later used for a specific type of shield—a large rectangular shield that would completely cover the soldier just like that rock covered the cave door. What did Paul say about the purpose of that shield? “To quench all the fiery darts of the evil one.” Did you get that? It covers so well and is so heavy that none of those darts can get past it. So whose fault is it when they do? It’s ours because we stuck something out where it didn’t belong, or completely dropped the shield.
Now what about that breastplate in 1 Thes 5:8? That word is thorax which is now our English word for “chest.” No, it doesn’t cover the whole soldier like the shield, but it does cover all his vital organs, and it does another thing as well. A thorax was a piece of armor with two parts, covering both the front and the back. Faith is like that. It will help you with the attacks you see coming—and sometimes you can see your problems rushing head-on—but it will also protect you from surprise attacks from the rear. Sometimes life deals you an unexpected blow—“didn’t see that one coming,” we often say--but your faith can protect you from even those sorts of things.
So is faith a shield or a breastplate? Faith is both, depending upon the point you are trying to make. The thing the two metaphors have in common is protection. God has given us what we need to stay safe. Don’t get so busy trying to explain things that shouldn’t need explaining that you forget to use it.
Put on the whole armor of God, that you may be able to stand against the schemes of the devil. For we do not wrestle against flesh and blood, but against the rulers, against the authorities, against the cosmic powers over this present darkness, against the spiritual forces of evil in the heavenly places. Therefore take up the whole armor of God, that you may be able to withstand in the evil day, and having done all, to stand firm. Ephesians 6:11-13