Question 48: What is the church?
Answer: God chooses and preserves for himself a community elected for eternal life and united by faith, who love, follow, learn from, and worship God together. God sends out this community to proclaim the gospel and prefigure Christ's kingdom by the quality of their life together and their love for one another.
Why hasn't Jesus Christ returned to earth yet? Although we cannot know all the details of God's hidden plan, one thing we can affirm is that God is allowing more time for people to repent of sins, believe the gospel, and be saved from his coming judgment (2 Pet. 3:9). As long as we are in this present age awaiting the second coming of Christ, we have a mission to fulfill, and that mission is to take the gospel to all nations of the world (Matt. 28:18-20).
God could have chosen to save people in any number of ways. He's God, so he is not limited in his abilities. If he wanted to communicate the gospel by writing it across the sky, or by sending angels to visit personally every human being on earth, or to impress the content of the saving message of Jesus immediately on every person's consciousness, he certainly could have done so. But God has chosen a method of gospel communication that would seem (at least to us), far less efficient, and perhaps far less effective, than those other means we could imagine. God has ordained that the gospel would be carried around the world by human messengers (Rom. 10:13-17).
I don't know all the reasons God chose to do it this way, but it seems that he delights in the human element of gospel proclamation. Just as he himself became a man in order to reveal himself most fully to us through the Incarnation, so has he ordained that it would be men and women, flesh-and-blood human beings, who would have the responsibility and privilege of representing him to the nations. And thus the church of Jesus Christ always has a mission, until the end of the age: to proclaim the gospel of Christ, making disciples of all nations, baptizing them and teaching them to obey all that Christ commands.
There are many good things that individual Christians can and should do in order to love their neighbors well and help improve society: fight against poverty, abortion, oppression, and injustice in every form while promoting the advancement of virtue, the institution of the family, strong neighborhoods, education, access to medical care, etc. As members of society, Christians should seek the good of society. But the church itself, as an institution, has one focused mission, and that is to make disciples of Jesus through the proclamation of the gospel. The extent to which local churches are distracted from that mission by being drawn to other good endeavors that are not, in fact, the mission of the church is the extent to which churches will fail to obey Christ. As the church of Jesus Christ, let it be our ambition to proclaim the good news to the world.
Suggested passage for personal or family reading: John 20:19-23. What does this passage tell us about the mission of the apostles and, consequently, of the mission of the church? What is the role of the Holy Spirit in our mission?