It seems to me that, in the case of Christianity, you have to consider a couple of things:\n\nFirst, you base your spiritual belief on what YOU HEAR: "So then faith cometh by hearing, and hearing by the word of God." Rom 10:17)\n1 John 5:10 (King James Version)\nKing James Version (KJV)\n\nThen, if you have faith, you'll have the withness IN YOURSELF:\n"He that believeth on the Son of God hath the witness in himself: he that believeth not God hath made him a liar; because he believeth not the record that God gave of his Son." (1 John 5:10). This refers to the Holy Ghost. As a matter of fact, the HOLY GHOST is our source of spiritual knowledge:\n"But the Comforter, which is the Holy Ghost, whom the Father will send in my name, he shall teach you all things, and bring all things to your remembrance, whatsoever I have said unto you." (John 14:26)\n\nThe Bible is the repository of the Word of God. It is a coded book, you need the "key" of faith and the  understanding given by the Holy Ghost to be able to "decode" the message in it.\n\nIn my opinion, it is the Holy Ghost who gives you assurance that what the Bible says is true... So although externally we base our spiritual belief on what the Bible says, the Holy Ghost tells us that what is in the Bible is true.\n\nPlease remember that some translations could be wrong, I believe that only the original scriptures are without errors. The Holy Ghost can guide us through all this errors to the Truth (if we let Him to teach us, I mean if we listen to Him).\n\nIN SUMMARY, I do base my spiritual beliefs on the Bible, but with the aid of the Holy Ghost, who guides me and teachs me what is true and what is not true about what I read from the different existing translations of the Bible, AND from the different interpretations that people (e.g. pastors) may have  on what the Bible says.