In Waiting for Godot, the theme of "illusion versus reality" figures prominently. In one sense, the line between illusion and reality/truth is completely blurred. In a seemingly chaotic, illogical world, Didi and Gogo find it difficult to make sense of anything and therefore can not distinguish between what is real and what is illusion.
At the beginning of the play, the two men can't remember what they did yesterday. Estragon (Gogo) thinks they were at the same spot yesterday but does not recognize the place. They are unsure (vague at best) about why they are waiting for Godot but continue to wait nonetheless.
There are no familiar character types, no familiar plot, nor any common situations to which the audience can relate. The language, the situations, and the characters are all presented in an illogical, absurd, or hopeless light. Given that the characters and events are so absurd, the play seems like a dream or nightmare. Therefore, the characters and the audience both experience what it is like to endure an absurd existence, unsure about what is real and what is illusion.
At the end of the play, Didi and Gogo plan to commit suicide "unless Godot comes." They also determine to leave but do not move. This indicates that they will repeat what they have done. This is why many have said that this is a play in which nothing happens . . . twice. Or, it is a play in which nothing happens over and over again. The fact that they presumably will not commit suicide, nor leave this place, indicates that they can not escape from their existence. And this is an existence which, when stripped of linear structure and traditional character roles/behaviors, is so bizarre that it is difficult to say whether it is real or a dream.
One implication of the blurring between illusion and reality is that the audience/reader might consider the ways of speaking, daily activities, and rituals that we do without thinking. Even if we were to question them, we might (as Didi and Gogo do) continue to do them. This might lead one to ask if these daily activities are truly meaningful or are they part of a self-created or socially created existence. In other words, Vladimir's and Estragon's world seems surreal and dreamlike but it might be more real in the sense that it is not structured with constructions such as plot, familiar roles, and linear progression. Without those constructions, are we (humanity in general and/or audience members) merely just waiting for these kinds of structures and constructions as Didi and Gogo wait for Godot? Does real life have a plot? Are these structures such as plot and identity real or illusions?
In Act 2, Vladimir indicates that their waiting has yielded nothing. It has only passed time.
We are no longer alone, waiting for the night, waiting for Godot, waiting for . . . waiting. All evening we have struggled, unassisted. Now it's over. It's already tomorrow.
A bleak interpretation of this play is that reality is waiting and anything beyond waiting is illusion and construction. Thus, the play is more real than our "reality." This is just one interpretation of the theme of illusion versus reality. In any interpretation, Beckett challenges the audience to consider what "real" means and/or what it means to exist or to be human.