Finding the church

We believe in one holy catholic, and apostolic church.

That's a traditional definition of the church, from the Nicene creed. Catholic, Anglo-Catholic, and Eastern Orthodox use that as a frame of reference. The terms are ambiguous, and become ciphers in the hands of high-church partisans. They don't use those criteria to define the true church, but use their denomination to define the criteria. The criteria become mirror images of their denomination. 

Catholic converts and apologists like Bryan Cross harp on "the visible church". Where do you find the visible church? Protestants don't have a visible church. 

Here's another definition of the church:

They devoted themselves to the teaching of the apostles, to fellowship, to the breaking of bread, and prayer (Acts 2:42).

That's a nifty compact definition. A functional definition.

i) What constitutes apostolic teaching is illustrated throughout the Book of Acts. The apostolic kerygma centered on the mission of Christ. Key events in the mission of Christ, interpreted through the lens of the OT. And Luke's Gospel supplies background information.

Nowadays, the teaching of the apostles is preserved in Scripture. 

ii) "Fellowship" is a broad concept for the communal life of the church. Pooling resources as well as a common faith (cf. 4:32). Alms. Corporate worship. 

iii) Does "breaking of bread" (cf. v46-47) allude to the eucharist or ordinary communal Christian meals? False dichotomy inasmuch as that formal distinction didn't exist at the time. The eucharist was incorporated into common meals (cf. 1 Cor 10-11).

iv) Private and corporate prayer have always been fixtures of Christian life, a carryover from Judaism. That's illustrated in the Book of Acts, as well as other NT documents. 

This is where you find "the church". You find the church whenever and whenever you find groups of Christians who exemplify Acts 2:42, both inside and outside of church. 

For further reading:

Darrell Bock, Acts (Baker 2007), 149-51.

Craig Keener, Acts 1:1-2:47 (Baker 2012), 1000-1011. 

David Peterson, The Acts of the Apostles (Eerdmans 2009), 159-62.  

Eckhard Schnable, Acts (Zondervan 2012), 177-80.