The novel, set in the bohemian Paris of 1938, focuses on three days in the life of philosophy teacher Mathieu who is seeking money to pay for an abortion for his girlfriend, Marcelle.

The Age of Reason is concerned with Sartre's conception of freedom as the ultimate aim of human existence.

The work seeks to illustrate the existentialist notion of ultimate freedom through presenting a detailed account of the characters' psychologies as they are forced to make significant decisions in their lives.

As the novel progresses, character narratives espouse Sartre's view of what it means to be free and how one operates within the framework of society with this philosophy.

"[2] The Harvard Crimson published an unattributed review of the book which states "Sartre's new novel is a rare and welcome plant in a period that almost completely lacks a balanced combination of emotional intensity and maturity in its writers."