That is to simplify it extremely. Many people have died in the pursuit of settling this dispute. Arianism for example was a very strong school of thought within early Christianity, and it was violently stamped out in the wake of the Council of Nicaea, on which its ideas on the nature of Jesus was rejected. Various other Christian sects even today reject the notion of the trinity (keywords nontrinitarian and unitarian).
There isn't a single religious idea in existence which is common to all religions. Not even the existence of something divine. And schism is the direct and immediate result, as soon as the founder of the religion in question dies.
@ Hanna: as critical historical research (by theologians by the way, no need to look to atheists for that) shows, various parts of the New Testament, including passages within the gospels as well as whole letters of Paul and passages in others of those, are forgeries inserted at a later date to prove this or that point, especially in the attempt to stamp out the Gnostic scools of thought. So criticism is something any church even worth a little respect should show. It's not as if the Bible is a book that was written at a specific point in time. It is a changing collection of copies of material written over a span of hundreds of years, compiled from versions of texts which may exist in dozens of
different versions each. And compiled by different people in different times at that, so that not even the different versions of the Bible as used by the Eastern Orthodox Church, the Catholic Church and the Protestant Churches include the same set of books.