The Old Testament prophecies of the glories of the new covenant era teach us to look forward in faith to a stupendous pileup of grace at the culmination of human history. God's goodness to us has already been overwhelming, and much more is on the way.
But in order not to get tangled up in more confusions about the relationship between the Old Testament and New, we have to grasp three things about all this. First, we have to understand that the glory of the new covenant builds gradually and inexorably throughout the new covenant era. Second, we have to recognize that we do not know exactly when in the new covenant era we have been privileged to live. And third, we have to understand that this is promise, not law.
But before considering those things in turn, we should refresh ourselves (in both senses of that word) by looking at just a couple of the promises.
"And it shall come to pass in the last days, that the mountain of the Lord’s house shall be established in the top of the mountains, and shall be exalted above the hills; and all nations shall flow unto it. And many people shall go and say, Come ye, and let us go up to the mountain of the Lord, to the house of the God of Jacob; and he will teach us of his ways, and we will walk in his paths: For out of Zion shall go forth the law, and the word of the Lord from Jerusalem. And he shall judge among the nations, and shall rebuke many people: And they shall beat their swords into plowshares, and their spears into pruninghooks: Nation shall not lift up sword against nation, neither shall they learn war any more" (Is. 2:1-4).
"The wolf also shall dwell with the lamb, and the leopard shall lie down with the kid; and the calf and the young lion and the fatling together; and a little child shall lead them. And the cow and the bear shall feed; their young ones shall lie down together: And the lion shall eat straw like the ox. And the sucking child shall play on the hole of the asp, and the weaned child shall put his hand on the cockatrice' den. They shall not hurt nor destroy in all my holy mountain: For the earth shall be full of the knowledge of the Lord, as the waters cover the sea. And in that day there shall be a root of Jesse, Which shall stand for an ensign of the people; To it shall the Gentiles seek: And his rest shall be glorious" (Is. 11:6-10).
Just in passing, we know that these prophecies are about the new covenant era, and not, say, about life after the Second Coming, because the apostle Paul quotes this last section from Isaiah 11 in Romans, using it to justify his proclamation of the gospel to the Gentiles two thousand years ago. So we know that all this glory is for us -- but how?
The Bible teaches in multiple places and ways that the kingdom of God arrives quietly, silently, unobtrusively. It does not arrive like the 82nd Airborne, wham. The rock grows to become a mountain that fills the earth (Dan. 2:35). The mustard seed grows from a tiny beginning into a great plant (Matt. 13:31). The yeast works its way through the entire loaf gradually, slowly, and how did that happen (Matt. 13:33)? Who saw that coming?
And this means that the kind of person who could tell a difference between the old covenant era and new covenant era by reading the newspapers in 50 B.C. and 50 A.D. respectively is the kind of person of faith who, like Abraham, could already see the city whose maker and builder is God. The progress of the gospel is such that there will come a time when everyone will be able to see it all with our eyes, and read in the newspapers about how West Point has been turned into a plowshare manufacturing factory. But before that happy day, there have been many periods of new covenant history, surrounded by smoke and ruin, when it was most necessary to cling to these promises by means of an Abrahamic faith. The kingdom of God comes in a slow build. The kingdom of God is a pot on the stove coming to a full boil, and each bubble is a century.
Why is this important? If it is not understood, then there will be a tendency to poke the eschaton in the ribs and tell it to get a move on, which relates to the second point. Suppose for example that God has determined that the new covenant era will last for 25,000 years. Now, for the next phase of our thought experiment, suppose that He has determined that the time will be 2,500 years. In the first scenario, we are still part of the early church -- living as we do in the first eight percent of the whole shebang. But if we are in the year of Lord 2009, and the whole thing will be over just 491 years from now, and it ain't gonna be that long, it makes more sense for us to put the shoulder down and push a good deal harder. But we do not and cannot know which one it is.
A woman in her ninth month having contractions should be at least thinking about how she is going to push. But if a woman starts doing that halfway through the first trimester, she is fixing no problems and creating many.
Those who would immanentize the eschaton in a comparable way will make us suckers for every other utopian scheme, and they will do to us what utopians, dreamers, and sectarians consistently do, which is to create bloodbaths. Pacifism is a sectarian way of overrealizing our eschatology. The pacifist tells the woman that "if you are pregnant, you should be pushing," and it hard to imagine a more pernicious approach. There will come a time when the need to push will become obvious and, past a certain point, inevitable and beyond debate. Which leads to the third point.
We understand that a promise is fulfilled when it fulfilled. We are not to look at promises that have not yet manifested themselvesin fulfillment, turn them into a law, and then try to make them true. The promise is that our children will one day play with cobras, and not that we are in sin if we don't send them out to play with snakes this afternoon. When will we do this? Gloriously, we will do it when it safe to do. When will the wolf and lamb lie down together? When they both want to, that's when. This is promise, not law.
One of our natural temptations is that of turning indicatives into imperatives. God tells us what He is going to do, and so then we try to figure out ways to do it for Him. Whenever we act like this, we consistently gum it up.
So when will we shut down West Point and Annapolis, and study war no more? When the promise is given into our hand. It will happen when the defenders of keeping the academies open are embarrassed by the fact that we haven't had a war for three hundred years, and the best argument for continuing is that of not wanting to abandon the honored and sacred tradition of the Army/Navy football game.