I've been thinkiing a lot lately about where naruto came from, like his history.
The only explaination that makes sence is that he is the 4th, when the 4th made the jutsu to trap kyuubi's soul how could he transfer it to naruto.
He probably found some way to give up most of his soul to the death god but left the basic part behind.
So he lost all his memories and techniques, and also changing him into a bady form (Naruto).
All the history about 4th dying is all made up to protect him while he's Naruto.
Thats what i reckon anyway.
If anyone has a better theory let me hear it