Why Did John Write?

John's statement of purpose for writing his Gospel explains that while Jesus did many things which were not written, it is that which is written which will produce saving faith. Though John speaks of his own writing, what he says is true of all of Scripture. That is, Scripture is sufficient; it is a 'more sure Word,' standing above all other truth in its authority and certainty. It is 'more sure,' than even what we gather firsthand through our own senses (2 Peter 1:19). Therefore, Scripture is the highest and supreme authority on any matter to which it speaks. Scripture is therefore the perfect and only standard of spiritual truth, infallibly teaching all that we must believe in order to be saved, and all that we must do in order to love and glorify God.