Traditions, Globalisation, Indoctrination and Zeal
Each Christian denomination has what I would call it's own tradition - its own set of distinctive beliefs, practices and ideas which characterize it and which it passes onto the next generation. Thus there is the Roman Catholic tradition, the Reformed tradition, the Baptist tradition, the Eastern Orthodox tradition... etc.
Historically the interactions between different Christian traditions have been quite limited. Generally, for example: If you were born a Lutheran you would die a Lutheran, and likewise for all the other traditions. Depending on where in the world you were born, and what your parents happened to think, you would grow up within a particular tradition. As such you would be taught their views on doctrine, their practices. You would be provided by your tradition with a set of saints or heroes of the faith. You would inherit with this tradition a particular doctrinal enemy(s) - a short list of one or two other traditions whom your tradition had historically 'fought' with on doctrinal or practical issues. And thus life went on. Few were the people who journeyed far outside the boundaries of own traditions. For the most part, this was unavoidable. It was, for example, pretty impossible for a person living in 18th century England to learn about or attend an Eastern Orthodox church.
However, I am inclined to feel the notion of traditions is rather crazy. To give an example, I understand one of the major differences between Luther and Zwingli was over the issue of the Lord's Supper and to what extent the elements really are the things they represent. As a result, two different traditions stem from that point, one following Luther's view and one Zwingli's. But what are the chances that a person born into Luther's tradition would happen to agree with Luther? Or what are the chances that a person born into Zwingli's tradition would happen to agree with Zwingli? Imagine if all subsequent people born, instead of being born into one of the two traditions at random by an accident of birth, were to seriously study the issue for themselves and then choose who they agreed with. There is no reason to think (short of some sort of extreme divine providence) that the people who would have agreed with Luther would actually be born Lutherans rather than into a family of Zwingli's tradition. As such, having two traditions ends up being somewhat of a nonsense - each tradition is filled with people who would quite possibly be in the other tradition if they studied the issues for themselves. But each tradition continues its theology and teaches its viewpoint onto its next generation nonetheless. The tradition continues only if it indoctrinates the next generation in its viewpoint and doesn't let them study the issues for themselves and go to the group they agree with most.
But with modern globalisation and the internet, things have changed. I live on an island in the pacific ocean and am a Baptist by birth, but it doesn't stop me discussing theories of the atonement with Reformed believers in England, nor from talking with Eastern Orthodox believers in America about the writings of the Church Fathers, or discussing general matters of theology on forums open to the entire world (or at least the English speaking, internet using, part of it) on a day-to-day basis. Likewise, Amazon.com delivers to my door books by Lutheran theologians, Roman Catholic scholars, Anglican bishops, Russian Orthodox writers and so forth. Never in the history of the world has it been easier to learn about other Christian traditions, read their very best writings, and dialog with people from those traditions on an ongoing basis.
I love discussing ideas with Christians of other denominations and hearing viewpoints I have never considered or heard before. I find hearing other viewpoints broadens my understanding immensely and stretches my mind and gives me a far better understanding of topics than I could ever get from one tradition or viewpoint alone. I love exploring different people's theological paradigms, seeing how they interpret the bible, how their theological ideas interact, how they practically apply their ideas. I'm a big picture person - I am interested in knowing as much of the wider picture as possible, as many different ideas as possible and seeing how they fit together. I enjoy tracing the historical development of doctrines, looking at the history of different traditions, seeing how their views changed over time and learning why they decided to believe and teach the things they do. I firmly believe that there is great benefit to be had in this. After all, given the number of different Christian traditions there are, the chances of the one you happen to have been born into (or converted into if your family wasn't Christian) being the right, true and correct one, seem minimal. And even if, by lucky chance you happen to be a part of the most-correct tradition, there is surely always room for improvement, and getting ideas from other traditions about what might be able to be improved within your own tradition is surely worthwhile.
But on a regular basis I am frustrated to encounter people who are zealous for their own tradition of their birth that they have been heavily indoctrinated in. These people are often extremely well-read... in their own tradition's writings. They have never encountered any serious arguments against their position, because they have never read any quality writings from any other traditions. Since they are well read in their own tradition's propaganda, they are utterly convinced their view is correct.