There are some essential things Christians must believe to be Christians.
If a so-called Christian does not believe these primary things, Paul says their faith is in vain, or worthless. Paul goes on in 1 Cor 15:1-8 to tell us what these are.
"For what I received I passed on to you as of first importance; that Christ died for our sins according to the Scriptures, that he was buried, that he was raised on the third day according to the Scriptures"Great problems occur when Christians do accept as believers others who deny the essentials. Problems also occur when Christians fail to accept in their church other believers due to disputable matters.
This is why Jesus himself prayed at the hour of his Passion, and does not cease praying to his Father, for the unity of his disciples: "That they may all be one. As you, Father, are in me and I am in you, may they also be one in us, . . . so that the world may know that you have sent me."
A denomination is a group of churches united in some way. Even good denominations can have some bad tendencies though. They can cause pride and reinforce extra-biblical beliefs as scripture (1 Cor 4:6-7, Prov 30:5-6). It is an error to equate an organization with the one body of Christ (Eph 4:4).
Denominations can also divide, confuse, and perpetuate error. Some groups may call themselves denominations, but even ones that do not may be just as divisive.
Some Christians think that denominations are a good and useful means to work together for the Lord. Other Christians do not see a need for them. Regardless of what a believer thinks though, 1 Cor 10:17 and 12:12-31 show we are all members of one body, and we should work together.
Paul said in 1 Cor 1:10-12, "I appeal to you, brothers, in the name of our Lord Jesus Christ, that all of you agree with one another so that there may be no divisions among you and that you may be perfectly united in mind and thought. My brothers, some from Chloe's household have informed me that there are quarrels among you. What I mean is this: One of you says, "I follow Paul"; another, "I follow Apollos"; another, "I follow Cephas"; still another, "I follow Christ." Is Christ divided? .Even a group that divided under the name of Christ was equally as bad as the other divisive Christians !!!!
We need to look at one another and decide that we will stand on the essential doctrines of the faith and that we will be united against the enemy.
Those of us who are united by the blood of Christ are not enemies with one another whether we be Catholic or Baptist or Protestant . It may be difficult for many of us to look lovingly into the eyes of those of a different denomination without thinking in our hearts that they are wrong about this doctrine or that doctrine. But, we need to be reminded that there is neither a Baptist nor a Catholic nor a Protestant on the throne of God !!
Lack of unity is a serious obstacle to the witness of evangelization. Division contradicts the truth of the Gospel, an essential element of which is the call to unity, so that non-believers who meet missionaries each preaching different versions of the Gospel will think it to be a source of division, despite its presentation as a way of love.
Rom 15:7 says, "Accept one another, then, just as Christ accepted you, in order to bring praise to God."
To summarize, we are to accept as fellow believers those God wants us to accept, and we are not to try to have unity apart from unity in the real Christ . The whole point is that we need to be united, not bickering. We need to move beyond the denominational barriers of what separates us into the common ground of what unites us: Jesus!