Why did knowledge of good and evil result in death?

In Genesis 2:17 God said to Adam: > "But of the tree of the knowledge of good and evil, thou shalt not eat > of it: for in the day that thou eatest thereof thou shalt surely die." > (KJV) Why did knowledge of good and evil result in death? Why is that kind of knowledge so deadly? How is this matter explained in Catholicism, Orthodoxy and main-stream Protestantism?