LitCharts assigns a color and icon to each theme in Nausea, which you can use to track the themes throughout the work.
Existence vs. Essence
Time
Love and Sexuality
Art and Legacy
Summary
Analysis
Roquentin writes a few pages on the Marquis de Rollebon, trying to keep a tight hold on his feelings after the excess of emotion he experienced on Sunday. He is growing increasingly tired of Rollebon. Roquentin feels frustrated with his inability to understand the Marquis completely or verify details of his life. He allows himself to imagine Rollebon, filling out the details of his personality in his mind. Roquentin realizes that this is a pointless exercise, however, since his work is based on research rather than imagination.
Roquentin’s work continues to grow less and less meaningful and satisfying for him. At this point, he begins to get frustrated with the limitations of his scholarly discipline. He has been interested in the Marquis as an idea, but as a historian, he’s forced to try to understand the Marquis as a person. In other words, his work deals with existence, but he finds his mind more often straying to the essence of the Marquis.