Jean-Paul Sartre (1905-1980) was the leading proponent of existentialism. Existentialism is rather abstruse, but a careful study of "The Wall" gives us insights into the philosophy and the man who wrote it.

"The Wall" tells the story of three men in a prison cell during the Spanish Civil War (1936-1939). The men were captured fighting against Francisco Franco's fascist army. Sartre, a Marxist, identified with the men's cause because Marxists fought against fascists during this war.

Existentialism is concerned with the nature of existence itself. The three men, told they would be executed the next morning, had to face this issue. They had to confront dying and how that reality shaped everything they had experienced during their lives.

Another central tenet of existentialism is choice. In The Wall, one prisoner, Pablo, is asked where Ramon Gris is hiding. Pablo is put into a laundry room for 15 minutes to think it over. This illustrates the importance of choice. Should Pablo tell to save his life or not? He decided to deceive them by telling them that Ramon was in the cemetery. The soldiers went out, found Ramon, and shot him. Ramon had, by accident, been in the cemetery!

This leads to another precept of existentialism: accepting responsibility for one's choices. Pablo, unlike his two companions, was not executed. But he had to face the reality that what he did led to the death of Ramon.

Although existentialism is a complex topic, a careful study of The Wall can elucidate its main components.

Let's begin by clarifying what "existentialism" means. It was a term coined by the French philosopher Jean-Paul Sartre (although it arguably has older roots) and is exemplified in a number of his novels (including Nausea and No Exit). Sartre also addresses it in non-fictional philosophical treatises (Being and Nothingness, for example). For an existentialist neither metaphysics nor morality offers a complete picture of a human being; the problems that dominated philosophical thought in the early twentieth century usually fell into one or the other of those categories. On the one hand, metaphysicians attempted to identify the nature of an individual, the relationship between mind and body, etc. and on the other hand, moral philosophers attempted to answer questions about how individuals should act. Neither is to be completely abandoned but neither is sufficient for answering the basic questions about existence.

Existentialism offers a third alternative. According to Walter Kauffman:

“Existentialism,” therefore, may be defined as the philosophical theory which holds that a further set of categories, governed by the norm of authenticity, is necessary to grasp human existence.  

Let us turn, then to the existentialist novel. One of the defining features of an Existentialist novel is that it will often not present a straightforward narrative but rather focus on a relationship or set of relationships — the character and the world, two characters, a group of characters, etc. — and explore them to the fullest. For Sartre, the social is created in the regard (look) of the Other; the Other views the subject in relation to himself and, in so doing, alienates the subject. For example, the subject is constituted as a woman via the resentment of a man. Sartre's novels, then, study individuals in society as he conceived of it. Existentialist novels also tend to revolve around a similar theme or set of themes – boredom, alienation, the absurd, freedom, and nothingness. Sartre's Le Mur (The Wall) follows such a pattern, both in its structure and with respect to the themes it addresses.

Existentialism is the term coined by Sartre to describe his perception of human existence. His form of existentialism is more properly called atheistic existentialism, and its followers believe that the individual is alone in a godless universe and that the basic human condition is one of suffering and loneliness.
All humans search for wholeness and well-being, existentialism doesn't hold out hope for humankind, the only way one can survive is to make their own set of values and live by them.
Juan, Pablo, and Tom all exhibit certain characteristics of men suffering an existential crisis. Juan pretends that what is going to happen to him is not. He refuses to walk to the courtyard and makes the guards carry him; he is passive in his own death. Pablo's sense of alienation keeps him from knowing his cellmates.Tom attempts to face death with honor, he tries to create his own values.