This lack of other sources ....
The Bible, the Greek word for books contains well over 60 books i believe and that is a lot of sources.
Who better to write an autobiography than the Divine being himself. After all, they cannot bear testimony that do not know Him.
However, from what I have read, the ideas that Christ embodied were not new ideas. That other older societies had the same type of "Saviour" of humanity. That perhaps the "Christianity" of today grew from these older sources and has long since forgotten its roots or these roots have been ignored.
As the bible says, He came that He might fulfill the law. So yess, smthg definitely existed. But why grasp at that which is incomplete. He replaced all other sacrifices to become the ultimate sacrifice.
If there was only one teaching of Christ then why are the so many differing interpretations of the bible by Christians? If the bible was divinely written as most say then why would God allow so many different interpretations? If i was God i know i would want to make damn sure people knew what I meant.
I think it was way back on the school playground that we all learnt that ppl will always interpret things to suit their own selfish desires. The bible even warns of this and says to be on the look out, even showing us how to spot them. Oh yea, He damn well wants to make sure we get it straight up.
The only place to truly learn about God is to read the Bible. U will find it deeply fulfilling