This is a takeoff from a discussion below about the fundamentals of the Christian faith. Fundamentals are the fundamental truths agreed upon by all Christians, no matter how much they disagree about church structure, baptism, eschatology, etc. etc. The fundamentals are the "lowest known quantity" you can reduce Christian faith to, in as few and clear words as possible.
The very interesting thing is that there were huge schisms in the early church in the 200's, 300's and 400's BC, before the church became solidly formalized into what later became the Catholic church. So you had the Trinitarians arguing with the Arians, and the Nestorians throwin in their unique perspectives, and the Donatists of North Africa arguing with Rome. All these groups differed significantly sometimes from each other, BUT....
The one thing they did was get together in Councils and hammer out the most basic short paragrpahs of common beliefs that united them all as Christians. Every word was meticulously crafted to include as many viewpoints as possible (even between the Trinitarians and Arians!) and to not exclude anyone unless they were outright flagrant heretics.
Because these basics were stretches as far as possible to accomodate differing Christian views, they have remained the standard as to what is Christian faith is and is not, for 2,000 years. Very few genuine Christians have ever felt the need to challenge these most basic creeds. The ones who repeatedly do so, however, are cults, who want to re-define God according to their quirky new gospel.