I was just in the shower thinking about how would I know "what is, is" wasn't? How would I know if it weren't true? (This was one trancey shower, let me tell you.) What if someone demonstrated to me that it was not a valid concept? What if that person were me -- what if became aware suddenly that "what is, is" didn't work? Would I feel threatened? Curious? Adrift? It was a great "get to nothing" question for me. I'm very clean now.