"Closure" is the missiological concept of finishing the task. Not everyone, however, thinks the Great Commission is a task that can be "finished" at a single point in time.
And some have defined "closure" in such a way that it makes it difficult to think it's possible.
Closure Conundrums is my series of blog posts (and maybe a book) on the challenge of understanding what "completing the Great Commission" actually means. This post is the first conundrum on the list. I welcome comments about aspects of this conundrum I haven't addressed (as it will inform the book).
Conundrum #1: We have reached closure when the world is _x_% Christian.
This seems obvious closure cannot be defined as 100% Christian. When Jesus said, "Go into all the world and make disciples of all the nations," we can't interpret this to mean "make everyone in every nation a disciple." Some chose not to follow Jesus (Pharisees, the Rich Young Ruler, the people in his hometown), and Jesus made it clear what happened to him would happen to us. The simple reality of promised persecution indicates not everyone would follow. To hammer it in, Jesus instructed his disciples what to do if the town rejected their message.
It also seems obvious that finishing the task must involve some people becoming Christ-followers. Jesus commanded us to make disciples, and he wouldn't command us to do something that was impossible.
So, we can know that when closure is reached, Christ-followers will number somewhere between 1 person and 100% of the world. And if that's the case for the world, it must be the case for any given place or people group.
Three alternatives might then be developed.
1) Closure is impossible since the world will never be 100% Christian. This is a straw man argument: we set up an unrealistic goal and use it to claim you can't interpret closure.
2) Closure is (or will be soon) finished, since we have 'made disciples' in every place/people. Usually this argument relies on some English rendering of a verse like Colossians 1:23, "if you continue in your faith, established and firm, and do not move from the hope held out in the gospel. This is the gospel that you heard and that has been proclaimed to every creature under heaven, and of which I, Paul, have become a servant" (NIV). But these sayings don't mean that literally every individual had heard; another rendering is "the Gospel has been preached all over the world" which is just a big statement meant to communicate it's not just for you. There are plenty of places and people that have not heard yet.
But there's an easier refutation for this: Jesus hasn't returned yet. Matthew 24:14 can be interpreted to mean his return is somehow tied to this commission (although there are problems with this, which I'll deal with in another post). Other Parables, like the Faithful Steward, tell us we should be working to make a profit for the King until he comes. The bottom line is: if trumpets haven't sounded, we should keep working.
3) Closure defined as a certain percentage in a certain place... We know that 'closure' will involve a percentage of Christ-followers between 1 and 100%. The problem is, of course - we don't know how many or who will respond to the call of Jesus. Making judgments about individual people is dangerous. Muslim imams and Hindu Brahmans and Buddhist priests and shamanistic witch doctors and even hardened atheists have followed Jesus, just as Paul the chief persecutor once did.
...so we get the apparently responsive few from the place and move on. While we cannot define "closure" or "the task finished" as 100% Christ-followers - nevertheless because of this problem our plans and strategies must be able to reach 100%, so as to encompass every individual who might respond to the call. (Because it might, for example, be 99.999% - and that's short of 100% of the current world population by just 70,000 people). Moreover, our plans must scale not just to 100% of the existing population, but 100% of the future population, too. Because: babies! But I'll cover that in a later Conundrums post.
...or we wait until we reach 100%. We have this idea that "closure" is not reached and so we can't go on to another place. But while we wait to reach a certain percentage that might never be attained, others are living and dying without hearing once hearing Good News. The problem with this approach is the Myth of the Scarcity of Gospel Workers, which says we only have so many people and so we argue about where to place them. That, too, is the topic for another post.
It nevertheless seems that we cannot define closure as a certain number or percentage of Christians, since Scripture gives no indication in the verses related to the Great Commission of what the response might be. The best we have is in Revelation, which has an image of every tribe, nation, and tongue before the throne (which is why we make lists). But we don't know how these "tribes" are defined. It seems language is important, and governments, and cultures. But more on this later.