The artist and his painting
Can't we learn all we need to know about God by observing His handiwork in the world? Can't we know how God wants us to live by getting in touch with our inner promptings or conscience? Why do we need the Bible? Imagine looking at a painting by an unknown artist that you've never seen before. You probably could have a reasonably intelligent discussion with someone about what the artist was intending to convey, just by looking at the painting. Now imagine that the artist walked into the room where the painting hung and began to talk about his painting and answer questions. Wouldn't your understanding and appreciation go to a whole new level?