What is the theme in The Jungle by Upton Sinclair?

I think that socialism is a larger theme in the book. Sinclair was exposed to Socialist politics as a young writer and became an apologist for the ideology. Sinclair illustrated the evils of capitalism in the book. Jurgis, his family, and the other workers were treated as expendable baggage by the companies. It is not until near the end of the book that Jurgis desovers meaning, identity, and worth through Socialism.