The Bible is sufficient. One does not need another book, a person or experience to guide one's life. The Bible is trustworthy. Since God inspired every word of it, it has no mistakes or contradictions. The Bible is intertwined.
Every scripture is linked to another.
There is no such thing as an isolated scripture. The Bible is Spiritually discerned. The carnal man can not understand it. God' spirit reveals and guides into all truth. The Bible is doctrinally sound.