The church knows it was not chosen because it deserved to be, but only because God is a God of love and grace. For the children of Israel were the church of the Old Testament and it was not because they were the largest nation, or the best nation that they were chosen, but just because God loved them. The church is not a casual banding together of people who have decided that it would be a good thing to worship God together. The church was brought into being by God as a part of His redemptive work. The present function of the church is to do the work of God in the world. Except when it is faithful to this function, it is not the church. Emil Brunner says, “The church exits by mission as fire exists by burning.” That is to say that when the church ceases its mission, it ceases to exist as a church, just as fire ceases to be fire when it stops burning.
The mission of the church is to proclaim the Kingdom of God, and summon men to its rule. The church itself cannot bring in the Kingdom. The Kingdom of God is already established. The church merely announces that this is so, and summons men to be subject to it. Just what this Kingdom of God is, will be the next topic, so we won’t talk about it now.
The mission of the church is actually in two parts. It moves in two directions. One movement is outward into all the world to proclaim a message where it is not known. The other movement is inward to clarify the message already heard. For the church is responsible for reaching out-and-out until the circle of its fellowship and the limits of the world coincide. It is responsible for reaching in until each person in the fellowship reaches his highest fulfillment. If the church was formed by God to implement His plan of redemption, then the church is performing its function in this plan when it reaches both outward and inward.