Waiting for Godot

Are Pozzo and Lucky foils for Vladimir and Estragon? How do the relationships of the character pairs reflect one another?

The tree without leaves is one of the few parts of the sparse staging that the characters explicitly mention. What symbolic meaning does the tree hold in the context of the play?

The characters frequently ruminate on religion throughout the course of the play. To what extent would you consider Waiting for Godot to be a religious play?