Bruno Bauer
One of the most frequent targets of critique in The German Ideology, Bruno Bauer was a 19th-century German philosopher, a student of Hegel, a radical rationalist, and a critic of religion, mainly Christianity and the Bible. He was a key member of the “Young Hegelians,” a German philosophical school that Marx attacks ruthlessly, both in this text and others.
Ludwig Feuerbach
Feuerbach, though not a member of the Young Hegelians, was an important post-Hegelian German philosopher and a significant influence for the group. Today he’s best known for his book The Essence of Christianity, in which he argues in favor of radical secularism, atheism, liberalism, and materialism, and as the object of Marx’s extended critique in his important work "Theses on Feuerbach." Though Marx is highly critical of Feuerbach’s form of “materialism,” unlike many of the other thinkers mentioned in The German Ideology, however, Marx does find some value in Feuerbach’s thought, and there’s evidence that his work did in fact influence Marx’s own.
The Bourgeois/Capitalist
Though often translated as “middle class,” references to the bourgeois or the bourgeoisie are better understood as analogous to references to capitalists and the capitalist class. Succinctly, a capitalist is an individual who possesses capital, which isn’t the same as being rich or having a lot of money. Specifically, a capitalist is someone who makes their living by (and whose function in society is to) use their money to make more money (in the form of profit). This applies equally to those whose money produces more money for them via investments in, as a contemporary example, Wall Street or real estate speculation, and to those whose investments take the form of factories, warehouses, machinery, offices, or any other means of production that allow them to command the labor of others.
The Proletariat
A key term of Marxist thought generally, the proletariat can, in a limited sense, be understood as the protagonist of Marx’s political thought. The term refers, essentially, to the working class, but the term is meant to be specific to the working class that exists under capitalism: those who must work for wages in order to survive. Though throughout history there have always been classes of people who performed the majority of the monotonous, grueling labor, and whose livelihoods depended on performing this labor, the modern proletariat is different in several ways. Rather than being subjected to any particular master, the proletariat is theoretically “free” to sell their labor to any capitalist. This, to Marx, results in an appearance of increased freedom, though in fact the compulsion to sell one’s labor in order to live is just as oppressive as serfdom.
