In are trying to hide their existence from themselves.

In the novel Nausea, Antoine Roquentin feels that
something has changed in the way he sees objects, but he doesn’t understand why.
He remembered that he felt weird when he was holding a stone, but he was not
sure if the feeling came from himself or the stone. He recalled the strange moment
as “nausea to the hands”. Roquentin thought that the weird feeling towards objects
and people only happened when he was alone or walking in the street, but this
time, he also felt the feeling when he was in a café. He also felt the Nausea because
of a blue cotton shirt which stands out joyfully against a chocolate-colored
wall. Roquentin also felt the nausea when he looked at the bartender’s purple suspenders,
which he thinks sometimes appear blue. He then realizes that the suspenders
were never purple, and that color is something that doesn’t really exist.  He then found out that he only sees hands,
eyelids, hair, cheeks, dirty skin, and enormous nostrils, and that he no longer
recognizes people. He requests the barmaid in the café to play his favorite
song called “Some of these days” to help calm him down. When the song started
to play, it successfully made the Nausea go away, he writes that the melody of
the song crushes the time of the real world, making him feel in the music. Roquentin
also felt more comfortable in the dark, because he thinks that the Nausea occurs
in the light. When in a café, he got disgusted at the behavior of the people around
him, which he describes as robot-like, because he thinks that the people are
trying to hide their existence from themselves. He then understands what was
causing the Nausea: his fear of existence. Things just exist and anything he
touches no longer has any essence. He described that the Nausea was a result of
colors, tastes, and smells that are not real. He finally understood what was
causing the Nausea when he encounters the root of a chestnut tree. He finds that the root’s physical characteristics mask
the root’s actual existence. Roquentin’s Nausea was because of Satre’s belief
of “existence precedes essence.” Anything used to describe an object is not
only irregular but does not really exist.