Our call as disciples of Christ is to be the Church God has meant for us to be.
And our call as a church is to make known the wisdom of God in His rich variety (Ephesians 3:10)
Intrigued by this common mission and the great variety of kinds of churches that have developed during the centuries, I wrote my Senior Seminar Paper at Great Lakes Christian College on which marks could be called the essential marks of the church.
I identified five of them.
2. Presence of the Holy Spirit
I would like to continue sharing my thoughts about the fourth mark: Separation.
"Discipleship and submission to God’s revelation call for separation.
This mark is evident from the very beginning of the Biblical story. Abraham is told to come out to separate from his family and culture. Israel is called out of Egypt, to separate from the Canaanites and the ways of all the other nations. The border laws in Leviticus define the separation of the nation of Israel from the other nations. Jesus calls the disciples to leave their fishing nets, and the Epistles call for a separation from the world.
Speaking of this separation, Jesus and the writers of the New Testament often speak also about the suffering that comes with it. The church should expect to suffer when it lives out the separation obedience implies.
This division between the children of the Kingdom and the children of the evil one (Math 13) is a clear expectation.
It was evident in the first century during the time in which the church was a persecuted minority, it lost its meaning for centuries after the Constantine period, and it is constantly at risk whenever the church attempts to bridge the gap with the world by adopting its values and norms.
The church needs to recognize this separation and seek the insight to live as a redeemed community in a fallen and broken world.
This will entail participating in life based on a different set of values shaped by God and empowered by the Spirit."
 Craig Van Gelder, The essence of the Church: A Community Created by the Spirit (Grand Rapids: Baker Books, 2000), 81.