The themes that apply to the Odyssey are 1) too much pride is dangerous, and 2) great journeys often lead back home. These are themes because these make up the general idea of the book. All of the other answers are either too specific or incorrect when looking at the plot of the novel to be true themes. Hubris (excessive pride) is a reoccurring issue and theme of the book, and the end of the hero’s journey ends with him back at his home in Ithaca, therefore, those are the two themes.
