I was on an online seminary forum a few years back, studying Systematic Theology, when I posed a disturbing question:
"Is there sin involved in denominationalism?"
It's the kind of question that sticks in your craw, gnawing at the edges of your consciousness, leaving you staring at the ceiling while clutching your covers in bed at night. (Or maybe it's just me.)
Anyway, the professor felt that this must not be just a rhetorical question, so he proceeded to say that yes, there is sin involved in denominationalism. He believed their very formation does indicate a break in the unity of the Big-C Church, which is called to be one, but there is no sin in being a part of a denomination. There is no sin in belonging to a Body which holds to a particular way of interpreting Scripture and lives out its faith in a communal way.
But here's another mind-bender:
What if God is so vast and so mysterious, that he actually cannot be explained by one Christian Tradition's preferences and interpretations of scripture? What if the very existence of different denominations testifies to his glory, to the wild, wooly wonderfulness of his Kingdom breaking in?
That is the question I would ask if I were in seminary now. Richard Foster begins to answer this question in his book Streams of Living Water: Celebrating the Great Traditions of Christ. In it, he references a mighty river of the Spirit breaking forth at this time in history:
The astonishing new reality in this mighty flow of the Spirit is how sovereignly God is bringing together streams of life that have been isolated from one another for a very long time. This isolation is completely understandable from a historical perspective. Over the centuries some precious teaching or vital experience is neglected until, at the appropriate moment, a person or movement arises to correct the omission. Numbers of people come under the renewed teaching, but soon vested interests and a host of other factors come into play, producing resistance to the renewal, and the new movement is denounced. [emphasis mine] In time it forms its own structures and community life, often in isolation from other Christian communities. This phenomenon has been repeated many times through the centuries. The result is that various streams of life — good streams, important streams — have been cut off from the rest of the Christian community, depriving us all of a balanced vision of life and faith. But today our sovereign God is drawing many streams together that heretofore have been separated from one another. 
It is Foster's assertion that the different streams of our faith—The Contemplative Tradition, The Holiness Tradition, The Charismatic Tradition, The Social Justice Tradition, The Evangelical Tradition, and The Incarnational Tradition—each teach us various dimensions of the spiritual life. That we should be students of these traditions and discover the ways they help us to imitate the life of Jesus.
All ways, means, and streams must point back to Christ, encouraging our imitation of him, transforming us yet deeper into his image. This is the end-game. And in this spirit, dissension flows away, believers begin to appreciate those dedicated to other Traditions, we allow God freedom to work and move in ways once foreign to us, we refuse snap judgments and yearn for prayerful renewal and careful lives modeled on ancient but relevant truth. "Out of the believer's heart shall flow rivers of living water" (John 7:38).
TODAY A MIGHTY river of the Spirit is bursting forth from the hearts of women and men, boys and girls. It is a deep river of divine intimacy, a powerful river of holy living, a dancing river of jubilation in the Spirit, and a broad river of unconditional love for all peoples. 
So be it! Yes, my stream and denomination could learn a thing or two. Always growing, always reaching, always seeking to become more like Jesus.
Your Turn: Describe your journey with Christian Traditions or denominations. Have you become open to experiencing other Christian Traditions—and how?
(Check out Foster's book for a visual of "Critical Turning Points in Church History" in chapter 1—a broad map of the movement of the early Church as it splinters and creates new streams and denominations.)
 Foster, Richard J. (2010-10-12). Streams of Living Water: Celebrating the Great Traditions of Christ (Kindle Locations 89-97). HarperCollins. Kindle Edition.  Foster (Kindle Locations 86-88).