"Ode to a Grecian Urn"

Keats has been on my mind for days. I miss English literature class. Never mind that the last one I took was over twenty years ago. I read "Ode to a Grecian Urn" because I could not remember the famous line. You know the one:
 "Beauty is truth, truth beauty---that is all 
  Ye know on earth, and all ye need to know."