Disdaining 19th-century notions that character development in novels should obey and reveal psychological law, La Nausée treats such notions as bourgeois bad faith, ignoring the contingency and inexplicability of life.
From the psychological point of view Antoine Roquentin could be seen as an individual suffering from depression, and the nausea itself as one of the symptoms of his condition. Unemployed, living in deprived conditions, lacking human contact, being trapped in fantasies about the 18th century secret agent he is writing the book about, shows Sartre's oeuvre as a follow-up of Dostoevsky's Crime and Punishment and Rilke's The Notebooks of Malte Laurids Brigge in search of the precise description of schizophrenia. Rilke's character anticipates Sartre's.
Roquentin's problem is not simply depression or mental illness, although his experience has pushed him to that point. Sartre presents Roquentin's difficulties as arising from man's inherent existential condition. His seemingly special circumstances (returning from travel, reclusiveness), which goes beyond the mere indication of his very real depression, are supposed to induce in him (and in the reader) a state that makes one more receptive to noticing an existential situation that everyone has, but may not be sensitive enough to let become noticeable. Roquentin undergoes a strange metaphysical experience that estranges him from the world. His problems are not merely a result of personal insanity, without larger significance. Rather, like the characters in the Dostoevsky and Rilke novels, they are victims of larger ideological, social, and existential forces that have brought them to the brink of insanity. Sartre's point in Nausea is to comment on our universal reaction to these common external problems.
Hayden Carruth wrote in 1959 of the way that "Roquentin has become a familiar of our world, one of those men who, like Hamlet or Julien Sorel, live outside the pages of the books in which they assumed their characters... . It is scarcely possible to read seriously in contemporary literature, philosophy, or psychology without encountering references to Roquentin's confrontation with the chestnut tree, for example, which is one of the sharpest pictures ever drawn of self-doubt and metaphysical anguish."
Certainly, Nausea gives us a few of the clearest and hence most useful images of man in our time that we possess; and this, as Allen Tate has said, is the supreme function of art.— Hayden Carruth