Read this excerpt from Endgame by Samule Beckett:
HAMM:
Go and get two bicycle-wheels.
CLOV:
There are no more bicycle-wheels.
HAMM:
What have you done with your bicycle?
CLOV:
I never had a bicycle.
HAMM:
The thing is impossible.
CLOV:
When there were still bicycles I wept to have one. I crawled at your feet. You told me to go to Hell. Now there are none.
What thematic idea does this passage most clearly help develop?