The three most basic Christian truths are:
(1) God actually exists.
(2) He has revealed Himself in a way that is understandable to people.
(3) His revelation has been preserved for us in the Bible.
2 Tim 3:16-17
All scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness so that the man of God may be thoroughly equipped for every good work.