What does it mean for Christ to be the church's cornerstone?

(Ephesians 2:20-21)

1. Jesus has given authority to the church, not individual Christians. (“A stone of testing,” Isaiah 28:16)

2. Those in the church trust, proclaim, and defend the gospel.
(“The foundation of the apostles and prophets”)

3. Christians cannot exist apart from the church. (“Being fitted together”)

4. The church is commanded to separate from and not formally associate with the world. (“Growing into a holy temple in the Lord”)