What are the main themes in Casablanca

You could examine several themes in the film.  One
overwhelming theme is the conflict between desire and duty.  Rick Blaine must decide
between his own self interests and the interests of the greater community.  In many
respects, such a theme can be applicable to the isolationists who felt that the
conflicts in Europe were "their problems."  Another theme that is present can be seen in
the political context, suggesting that repressive regimes have to go to extraordinary
lengths to maintain power.  General Strasser and the Nazis are only able to survive by
eliminating everyone who stands in their way.  While this is something that they were
able to do for a while, eventually, Laszlo finds a way out and the Resistance gains
strength, and undermines the Nazis.  The last theme might be an explorative one that
comes from Rick's last words to Ilsa:  "The problems of two people don't amount to a
hill of beans in this world."  The idea here is that the private concerns fade in
comparison to the public issues.  While this might be true with the ending of the film,
the reality is that the entire movie is motivated because of the private desires of
individuals.  Ilsa and Laszlo, Ilsa and Rick, Rick and Louis, and Rick and all of the
people at Cafe Americain help us understand the political climate of the time.  Yet, we
only know this configuration through individual interactions and "the problems of two
people."  While Rick's statement might be true and valid, there is an equal amount of
evidence to suggest that the problems of two people do amount "to a hill of
beans."