Been reading over Mark Dever's book 9 Marks of a Healthy Church and am continuing to struggle (though even before this book) with the idea of church membership. He advocates for it in the sense of active, consistent engagement with a local body, which I agree with, though I think in the background is the thought of documented membership, which is what I struggle with. I think being a dedicated participant in a local church is an important thing, but the idea of explicit membership requirements (classes, documents, etc.) make me think that we've so blurred the lines of what it means to be a Christian, much less look like one, that such things become necessary to identify the church or worse, to use as a measure to gauge the success of a local body. I think the prolific use of the phrase "invisible church" even more so highlights this problem. How do we justify uses of such phrases in light of the difference our lives are supposed to reflect when we follow Jesus? Do we look so much like the world that we can't tell who is the church? If we are invisible, are we really the church?
"Do not love the world or the things in the world. If anyone loves the world, the love of the Father is not in him. For all that is in the world—the desires of the flesh and the desires of the eyes and pride of life—is not from the Father but is from the world. And the world is passing away along with its desires, but whoever does the will of God abides forever." (1 John 2:15-17 ESV)
Do all things without grumbling or disputing, that you may be blameless and innocent, children of God without blemish in the midst of a crooked and twisted generation, among whom you shine as lights in the world, holding fast to the word of life, so that in the day of Christ I may be proud that I did not run in vain or labor in vain. (Philippians 2:14-16 ESV)
Love to hear additional arguments for or against the "explicit membership" requirements with a focus on what the Bible highlights as important for the church to practice in this regard.