What lesson do you think Beckett is trying to teach us in Endgame with his depiction of the lives of Hamm and Clov?

First, lesson
is not the right word to describe Becketts motivation for writing.  He had no interest
whatsoever in showing the world how things work.  is a stage description,
in stage language, of Becketts view of the Cartesian duality of mind/body.  Hamm and Clov are
two sides of a master/slave...