The themes are the major ideas in a piece of literature, often universal concepts that are explored in a story. In Martin Eden, one theme is the problem of social class structure. For example, Eden is a sailor from a working class background. When his skill and knowledge exceeds that of people from higher social classes, he feels isolated from those he formerly respected, and he is also distanced from the people in his own social class whom he used to be close to, because he is no longer like them.
Another theme is that of individualism versus socialism. Eden rejects socialism and becomes a self-made individual, rejecting the notion that one must work for the whole group instead of for himself alone. However, the author suggests that this drive for individualism leads to Eden's isolation and spiral downward until he commits suicide. Eden believes in individualism but the benefits of rejecting socialism also destroy him in the end.
One particular theme that emerges from London's work is how the artist is constructed. Martin Eden begins his pursuit of art with a sense of optimism. Writing can be a way for him to not only articulate his view of the world but can also reveal happiness for him. As he matures into an artists, it becomes clear that he is alone in the world. That which accepts him does so on phony and pretentious grounds. Ruth only accepts Martin because he is a success. Editors that rudely rejected him now beg for his work only because he is successful. At the same time, the artist is unable to go to a realm where they are not understood. Martin can no longer be with the sailors he used to be with because "Too many thousands of opened books yawned between them and him." He has become "removed" from such a reality. It is this same condition that prevents Martin from being with Lizzie. The artist is constructed as someone who is on the fringes of society as they cannot be embraced by that which does not understand them and are repulsed by the insincerity of those that do. This construction of an artist is a theme that drives the work, helping to explain why Martin commits suicide at the end of the narrative.