Truth and Sanity
Sanity, craziness, and truth are all important themes in the book, as well as important themes in the surrealist movement and they are all linked together. When André spent a lot of time with Nadja in the beginning of their relationship, he discovered more of himself and what the world really is like through the eyes of Nadja (or so he thought). A prime example was once when they were going for a walk, and Nadja pointed at a black window stating that it would turn red in just a few moments. As André watched, it turned red. Yet, as he thought back on the event, he wondered; did it really turn red, or did Nadja’s insanity take over Andrés mind? Or was everyone else insane to not see the change of the windows color?
Reality
Reality and truth are also heavily connected, as they can often be used as synonyms, however, it is also a whole theme on its own. Is reality relative, and if not, who decides what is real? In Nadja’s instance, she believed things that others didn’t, which was what initially intrigued André to her side, yet was also what landed her in a mental institute. As André pushed her away, he later looked back, wishing that he could have spent more time with her, as her reality was, in fact, also a reality.
The person
One of the first and maybe most obvious themes in the book is the philosophy of the person, the human mind and "self". Who are we really, and why are we on earth? According to André’s philosophy, people are “haunted” by themselves, or their “true” selves, which is what they/we are humans are longing to becoming, and working towards, if we are aware of it or not.