A very controversial question with many,many answers—— You know the text in Matthew 16 when Peter made his confession and Christ promised, I will build my church—– I decided that the church was whatever Christ meant when he used the word “church” and the church is what Christ is doing in history.Whatever Christ meant when he said “church”, whatever he is building in the world, that is my definition of the church. Begging the question? I think not. According to his own testimony, Jesus entered history to do the Father’s will— an agreement they had arranged before the foundation of the world. He said, “I will build my church!” I believe it! The church is the body of Christ!The church is the bride of Christ. It is what he is building in the world. He said something else—fundamental to understanding the church as He meant it: ‘The gates of hell shall not prevail against it.” In obedience to the Father’s will He is building something in history that is indestructible—the church! It is inconceivable that Jesus would refuse to do the Father’s will—and it is inconceivable that He could fail in what he is building! What humans build is temporal—vulnerable—perishable. That which Christ is building—whatever it is—is permanent and eternal. The Church is what Christ is building in the world. My desire is to be part of that. Matthew16:17-18 “Blessed are you, Simon son of Jonah, for this was not revealed to you by man, but by my Father in heaven. And I tell you that you are Peter, and on this rock I will build my church, and the gates of Hades will not overcome it.” Source; Wisdom of the Church by Richard C. Halverson Published 1995.