Sin?

I just started reading a book called "Disappointment with God" by Philip Yancey(look him up. he's a genius and an incredible author). The title of the book caught me by surprise but it also sounded like it might have some answers to some questions a friend of mine has been struggling with. I started reading it and realized it had even more answers for my own life. For instance we come to God, as Christians, expecting something in return but what we experience never seems to measure up to what we expect. He tells a story of a time when he begins mentoring a young(not just his age but his longevity as a Christian), brilliant Christian who is finishing up seminary and sends his thesis to be edited by him. He likes it so much he tells him to publish it. Shortly before the book is to be published the man comes to visit him. He has all of a sudden began to doubt what he has written and has lost all faith in God. Yancey listens to his story and soaks it in. He summarizes what he feels his motives are in three questions. Is God unfair? Is God silent? Is he hidden? I haven't read a whole lot but I'm gonna guess that he answers the questions. I've only read 4 chapters. Sound good? Then read the book!

Anyway, on a side note but really why I decided to write this at almost one on a Sunday morning. The questions he brought up made me think of one of my own. Why does sin exist? Since God created everything and knows about every detail of the entire universe why can't he just make sin disappear? I've had some thoughts but none seem to give me a solid answer.