Final answer:
Karl Marx believed the most significant factor to unite people would be class consciousness, leading to a global working class and an international dictatorship of the proletariat, resulting in a communist revolution.
Step-by-step explanation:
Karl Marx believed that class consciousness would be the most significant factor to unite people in the 20th century and beyond. This belief stemmed from his vision of a global working class that would transcend nations, races, and ethnic groups. Marx prognosticated that workers around the world, rather than being divided by religion or nationalism, would unite through their shared interests as members of the proletariat. He imagined a global working class eventually leading to an international dictatorship of the proletariat.
The core of Marx's theory was that the conflict between the bourgeoisie, who controlled the means of production, and the proletariat would intensify, resulting in a communist revolution. This revolution would end the exploitation of the proletariat and foster a classless society. Marx predicted that this proletarian revolution would spread internationally, uniting workers across different nations to form a classless, communist society with shared wealth and communal ownership of production.