Divisions in the church are a result of sin. Ever since Babel, mankind has been cursed with a sectarian spirit. Even the church in C1 Corinth, under the influence of the blessed apostle himself was riven by sectarianism. You'd have thought they'd all unite as a body under such infallible Scriptural teaching, but no. "I am of Paul" cried some, "I am of Apollos" shouted others, and still others "I am of Cephas".
How does Paul deal with such sinful division? In chapter 1:10-28 he appeals for unity under the message of the gospel.
I appeal to you, brothers and sisters, in the name of our Lord Jesus Christ, that all of you agree with one another in what you say and that there be no divisions among you, but that you be perfectly united in mind and thought.(v10)Yet later in the same epistle in verse 11:19, Paul concedes that divisions, sinful though they are, serve a purpose in the mysterious providence of God. These divisions serve to show "who have God's approval."
To highlight his point it's helpful to look at what Paul doesn't say. He doesn't say something like "In all your divisions you are each providing a different perspective on truth and piety. When all these perspectives come together, they form a wonderful, rich and varied tapestry highlighting God's truth." In other words, not every sect has something relevant to say. It's kind of trendy today to speak of the different denominations of the church as providing a manifold witness to the truth of the gospel. Yet such gobbeldygook rests upon a hermenuetic of uncertainty and an overly chastised epistemology.
For instance, how do the various strands of the church provide a different perspective on the truth of justification? Rome says faith plus works, Geneva and Augsburg say the opposite. Are both sides right? Rome speaks of two streams of revelation, Geneva and Augsburg speak of only one. Are both sides correct? Pentecostals affirm the continuation of supernatural prophecy, while those bound by the Westminster Standards deny this. Are both camps providing different perspectives on truth? Oh please. This type of crap is just a watered down version of postmodernism's maxim that all roads lead to God.
Or take church worship as another example. The Reformed believe in singing only inspired texts, while the rest of evangelicalism will sing anything but inspired texts. Are they both correct? Rome believes in the sacrifice of the Mass, while Protestants see it as a horrible blasphemy. Are they both following the leading of the Spirit? If the Spirit leads me to pray to Mary, while He leads you to embrace the exclusivity of Christ, is He playing games? Is he Bi-polar? Clearly not.
The purpose of divisions according to the apostle is to highlight those who are genuinely blessed by God (v19). The apostle believes that the validity of certain church practices should be self-authenticating. For instance, it's obvious that getting drunk during communion isn't pleasing to God, so those who abstain from booze during worship are obviously approved.
So to sum up, first, divisions in the church function as a mysterious providence as to who has God's approval; they don't all witness to different aspects of an unattainable truth. Second God's approval of certain parties among the divided is self evident. Third his approval rests upon those who uphold the purity of the gospel through right preaching of the word and proper administration of the sacraments.