1. "church" is probably not a particularly good word for translating what Jesus promised to build, "ekklesia", which is better translated as "community" or "assembly", or even better, "those called-out into an assembly" (which is admittedly somewhat unwieldy). The earliest translators of the Bible into English knew better than to translate the word as "church", but when King James gave his approval for an English translation, one of his 14 rules upon which he insisted was to keep the old Catholic words like "baptize" and "church", thereby keeping the baggage that goes along with those words.
The point is that Jesus didn't build an organization so much as he built an organism. It might seem like a minor thing, but the concept reaches far into how we perceive our mission.
2. The church of christ in Corinth had splintered into denominations. Paul said this shouldn't be, but even so, he considered these denominational members as saints, members of the church of God (1 Cor 1:2, 10ff).
3. The "church of God" is, as are many other terms, just as Biblical as "church of Christ".
4. In Acts 15:28, it "seemed good to the Holy Spirit" and to the church leaders and apostles, that the church be composed of two distinct groups, having different practices (one observed the law of Moses; one didn't). We see this same division elsewhere in the New Testament. Yet these two "denominations" were united as one body, united in spirit but not practice, nor even in name (e.g., "Circumcision" vs "Non-Circumcision). Even when one group sees a particular issue as sinful and the other group does not, the apostle instructs the "freer" group to sacrifice their freedom for the sake of the weaker group, without necessarily "believing the same things" (Rom 14). "Being of like mind" does not mean "believing exactly alike"; it means staying united despite having different ways of seeing things.
5. Any person properly converted is added by the Lord to his ekklesia. Even if that person mistakenly believes himself to be an Apollosite or a Baptist, he's still a member of the church of Jesus Christ, just one who is in error, like those Corinthian Christians. (But then, who of us is not in error in some unknown way, at some point in our walk with Christ?) Such a person should heed the call to come out of those man-made organizations, to be in nothing more than the called-out assembly of Christ.
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