The Theatre of the Absurd attacks the comfortable certainties of religious or political orthodoxy. It aims to shock its audience out of complacency, … - Martin Esslin

The Theatre of the Absurd strives to express its sense of the senselessness of the human condition and the inadequacy of the rational approach by the open abandonment of rational devices and discursive thought. While Sartre or Camus express the new content in the old convention, the Theatre of the Absurd goes a step further in trying to achieve a unity between its basic assumptions and the form in which these are expressed. In some senses, the theatre of Sartre and Camus is less adequate as an expression of the philosophy of Sartre and Camus — in artistic, as distinct from philosophic, terms — than the Theatre of the Absurd.

The Theatre of the Absurd … can be seen as the reflection of what seems to be the attitude most genuinely representative of our own time.  The hallmark of this attitude is its sense that the certitudes and unshakable basic assumptions of former ages have been swept away, that they have been tested and found wanting, that they have been discredited as cheap and somewhat childish illusions. The decline of religious faith was masked until the end of the Second World War by the substitute religions of faith in progress, nationalism, and various totalitarian fallacies. All this was shattered by the war.

The "poetic avant-garde" relies on fantasy and dream reality as much as the Theatre of the Absurd does; it also disregards such traditional axioms as that of the basic unity and consistency of each character or the need for a plot. Yet basically the "poetic avant-garde" represents a different mood; it is more lyrical, and far less violent and grotesque. Even more important is its different attitude toward language: the "poetic avant-garde" relies to a far greater extent on consciously "poetic" speech; it aspires to plays that are in effect poems, images composed of a rich web of verbal associations. The Theatre of the Absurd, on the other hand, tends toward a radical devaluation of language, toward a poetry that is to emerge from the concrete and objectified images of the stage itself. The element of language still plays an important part in this conception, but what happens on the stage transcends, and often contradicts, the words spoken by the characters. In Ionesco's The Chairs, for example, the poetic content of a powerfully poetic play does not lie in the banal words that are uttered but in the fact that they are spoken to an ever-growing number of empty chairs.