The major thematic contrast in the narrative is between?

I think Sinclair compare Socialism and Capitalism. Sinclair was exposed to Socialist politics as a young writer and quickly became convinced by the movement's premise. Socialism is an economic theory that promotes worker ownership of the resources of production. Sinclair came to see capitalism as a vicious system of economics that exploits the masses in order to make the elite few rich. Capitalists hoarded resources and wealth for themselves, while millions of workers and laborers suffered in poverty and dangerous working conditions.