I am a little uncertain, though, that this can be proven biblically. Can we really show that these are the only necessary marks of the church? What about evangelism? What about prayer? What about elders? Deacons? Are any of these necessary for being a church, or are they necessarily entailed in the three above?
Secondly, what if a church is not practicing some of the above? Are they not churches?
The Corinthian church was failing in its duty to practice church discipline. Did it cease to be a church? Is the Salvation Army and ultra-dispensational groups not churches because they don't practice water baptism? Should baptists and paedobaptists consider each other not true churches because they believe the other is not rightly administrating the ordinances/sacraments?