In the Diamond Sutra the Buddha dismantles the world view of his followers. He pulls the rug out from one concept after another. With the sword of wisdom he cuts and cuts. And still it is very difficult to cut away our own beliefs –  the thoughts we replay again and again. If it was a movie we would have walked out a long time ago, but our thoughts and our beliefs are seductive.  So, we know all about the world and how it works- we know all about ourselves and others but really all this knowing is just manure. Manure spread on the clean and beautiful snow of reality.
So practice is cleaning what is already clean.  But this takes great faith and intention. Which one of us has the drive and courage to sincerely put our faith in the Way.