What makes Jean-Paul Sartre's 'Nausea' a philosophical novel?

I know it's an existential novel but how is it particularly philosophical?|||Read it and decide for yourself|||From wikipedia:





Criticism of Sartre's novels frequently centered on the tension between the philosophical and political on one side versus the novelistic and individual on the other.





Ronald Aronson describes[16] the reaction of Albert Camus, still in Algeria and working on his own first novel, L鈥櫭塼ranger. At the time of the novel's appearance, Camus was a reviewer for an Algiers left-wing daily. Camus told a friend that he "thought a lot about the book" and it was "a very close part of me." In his review, Camus wrote, "the play of the toughest and most lucid mind are at the same time both lavished and squandered." Camus felt that each of the book's chapters, taken by itself, "reaches a kind of perfection in bitterness and truth." However, he also felt that the descriptive and the philosophical aspects of the novel are not balanced, that they "don't add up to a work of art: the passage from one to the other is too rapid, too unmotivated, to evoke in the reader the deep conviction that makes the art of the novel." He likewise felt that Sartre had tipped the balance too far in depicting the repugnant features of mankind "instead of placing the reasons for his despair, at least to a certain degree, if not completely, on the elements of human greatness." Still, Camus's largely positive review led to a friendship between the two authors.





G.J. Mattey, a philosopher rather than a novelist like Camus, flatly describes[17] Nausea and others of Sartre's literary works as "practically philosophical treatises in literary form."





In distinction both from Camus's feeling that Nausea is an uneasy marriage of novel and philosophy and also from Mattey's belief that it is a philosophy text, the philosopher William Barrett, in his book Irrational Man: A Study in Existential Philosophy, expresses[18] an opposite judgment. He writes that Nausea "may well be Sartre's best book for the very reason that in it the intellectual and the creative artist come closest to being conjoined." Barrett says that, in other literary works and in his literary criticism, Sartre feels the pull of ideas too strongly to respond to poetry, "which is precisely that form of human expression in which the poet鈥攁nd the reader who would enter the poet's world鈥攎ust let Being be, to use Heidegger's phrase and not attempt to coerce it by the will to action or the will to intellectualization."





The poet Hayden Carruth agrees with Barrett, whom he quotes, about Nausea. He writes firmly[3] that Sartre, "is not content, like some philosophers, to write fable, allegory, or a philosophical tale in the manner of Candide; he is content only with a proper work of art that is at the same time a synthesis of philosophical specifications."





Barrett feels[18] that Sartre as a writer is best when "the idea itself is able to generate artistic passion and life."





http://en.wikipedia.org/wiki/Nausea_(nov鈥?/a>