Abraham sought a city with foundations:

Hebrews 11:10 "For he looked for a city which hath foundations, whose builder and maker is God."

The Church has foundations.  It is built on the apostles who are built on Christ.

Let God be true and every man a liar.

Apostles are given the responsibility of protecting the entire flock of God from the attack of the enemy, but with so many voices in the world, each one claiming to be the one that should be listened to, how can you know? You are responsible to be close enough to God so that you can tell the difference between false apostles and real apostles.

Read the complete definition of "Apostle."