Instruction: Read the reading material, and answer the question.

Reading Material: Karl Marx, Introduction to Critique of of Hegel's Philosophy of Right

The following paragraph:

Karl Marx wanted to complete the transformation of Germany that Martin Luther began. He writes in today's reading, "Even historically, theoretical emancipation has specific practical significance for Germany. For Germany's revolutionary past is theoretical, it is the Reformation. As the revolution then began in the brain of the monk, so now it begins in the brain of the philosopher." Karl Marx is the philosopher who will start the next German revolution. He argues that Luther freed Germans from the authority of the Chruch, and so he will free Germans from the authority of all religion, including Protestantism. He thinks that German philosophy after Hegel has taken this attack upon religion as far as it can go, so that the next step is the actual destruction of religion in Germany. This will happen only if people rise up take over the state and abolish private property. But what people? Most of the essay for today explains why in France the middle class (the "bourgeoisie") could lead the Revolution against the King, and why in Germany the middle class cannot do this. He explains that in Germany the middle class is too modest, too polite, to make demands. Everyone thinks they have a special role to play in society, and they don't feel connected as a whole group. So Marx, at the end of the essay, says that in Germany the revolution will start with the "proletariat."

Question: What is the proletariat according to Marx? What does he mean when at the end of the essay he says that the proletariat "has a universal character by its universal suffering?