So Marx was writing in 19th century England, and there were two classes that mattered, the workers and the capitalists. The capitalists owned most of the factors of production, in this case, land and the capital to invest in factories. The workers just had their labor. So the class struggle here is between capitalists, who want labor at the lowest possible price, and the workers, who want to be paid as much as possible for their work. There are two key ideas that underlie this theory of class struggle. First, Marx believed that production, or work, was the thing that gave life material meaning. Second is that we are by nature social animals.