The theme of any literary work is the base topic or focus that acts as a foundation for the entire literary piece. The theme links all aspects of the literary work with one another and is basically the main subject. The theme can be an enduring pattern or motif throughout the literary work, occurring in a complex, long winding manner or it can be short and succinct and provide a certain insight into the story.

A thematic idea that would transfer into a them would be identity. We are told to allways remember where we came from. Captain Nemo follows by this and does not forget his roots.

20,000 Leagues Under The Sea