Immanuel Kant defined The Enlightenment as the overcoming of self-imposed immaturity. He suggested that this process was inevitable provided that society as a whole had obtained the freedom to use reason. In many ways this view of Enlightenment met its end in the thinking of Karl Marx who posited that the lack of maturity in society was the direct consequence of the material forces in any given mode of production whereby at least one social class must exploit one or more other social classes for its existence. In the Marxian view, the real Enlightenment will be the product of an eventual communist revolution and what Kant views as freedom is merely an illusion. While Marx appears to offer a stronger argument, his view of Enlightenment is rather vague on what is certainly one of the most important questions of philosophy, ``what does it mean to be a human being?''
Kant understood immaturity to be dependence on others, especially in the realm of reasoning. In his view people are immature when they look to others (pastors, professors, rulers, authors) for the formation of their thoughts rather than taking the time to think things through on their own. Kant was especially offended when the root of immaturity is the refusal of individuals to accept responsibility rather than an incapability of those individuals to think things through. The refusal to accept responsibility makes one's immaturity self-imposed.
Kant explicitly stated that this freedom deals with one's public life and not one's private life. He uses these two terms in a way that is confusing to we who tend to reverse their meanings. With regards to the private sphere, Kant means an individual's professional role. For example teachers, pastors or government officials would all be acting in a private capacity because they are representatives of their employers. In these types of roles Kant argued that one ought not to have the freedom to critically use reason because one is representing someone else. When serving in such a capacity, Kant argues that a person has been hired precisely to be doctrinaire and to toe the party line. But Kant does not believe that this restriction of intellectual freedom should extend to the public sphere where every individual is a human being with the right to critically use reason. In fact, Kant argues that one has not only the right to critically use reason but also has the obligation to apply reason in a systematic fashion in order to seek out the truth. In this view the schoolteacher by day follows the dogma set forth by the board of education but outside of the boundaries of the school day has the intellectual freedom to question, dispute and critique that very dogma.
When individuals do this on an individual basis, however, Kant observes that it is difficult and the results are not usually very impressive, akin to a single person leaping over a puddle of mud. But if all are made free and able to pursue the systematic application of reason, the results are society wide and each generation becomes more able to reason than the generation before. Kant conjectures that this process ends in the very changing of societal principles. The most important of these to Kant is the change in principles of governance whereby governments begin to respect the political rights of all especially with regard to personal autonomy and the freedom of individuals to pursue the application of reason.
But where Kant viewed political freedoms as the eventual end of the Enlightenment, Marx saw these same political freedoms as symptomatic of the lack of true freedoms. Marx based this view on a materialistic outlook of history where humanity is entirely defined by the totality of all social relations. Chief among these social relations in Marx's thought was the mode of economic production.
In Marx's view, the process of Enlightenment which Kant speaks of comes about as the consequence of a specific mode of production (industrialized capitalism) under which the owners of the means of production (the bourgeoisie) exploit those they hire (the proletariat) as laborers in order to extract profit. (Profit in the Marxian view arises because the owners of the means of production do not pay the laborers full value for their labor.) The illusion of political freedoms, Marx argues, fools the proletariat into thinking that they are free when in fact they are not. Marx holds out as evidence that they are not free the fact that because each labor thinks of his or her self as an individual rather than as a species-being, each laborer is fundamentally alienated from his or her own essence as a human.
Consequently, Marx desires not political freedom as the result of Enlightenment but actual freedom as the result of an actual revolution. Marx, the strict materialist, holds that material freedom rather than ideological freedom is the only true freedom. Further, he holds that material freedom can only exist when humanity is no longer alienated from itself as a species being. The largest aspect of this freedom is the freedom from having to continually produce as a means of continuing one's own existence. So long as one has to sell one's labor in order to acquire necessities as food and shelter, one is not free on a material level according to Marx. Hence, Marx holds that freedom, true freedom, will only come when there is no more class conflict and no longer will one or more classes exploit others.
A good example of Marx's views can be seen in his essay On the Jewish Question where he criticizes Bruno Bauer, charging that Bauer misguidedly chastises Jews for maintaining their Jewishness while seeking political rights. Marx's criticism is that the political rights sought by the Jews are merely the outward form of Christian ideology which is a theoretical application of Judaism. Bauer's mistake, Marx charges, is that he doesn't see that all religions are illusory and that the conditions that gives rise to the illusion of Christianity are also the conditions that give rise to the illusion of political rights. Consequently, if destroys a religion but not its material base, its form will remain. Industrial capitalism, Marx argues, is the material basis of Christianity and even if Christianity is destroyed, the material basis will remain and something very much like Christianity will simply take Christianity's place in the superstructure built on top of the economic base of industrial capitalism.
Marx's argument against Bauer rests upon the example of the United States. The US, Marx asserts, is an atheistic and democratic state based on fundamental political freedoms. But even though the US is secularized, the people of the US remain deeply Christian. Christianity has been removed from the government but continues to exist in the private lives of the citizens, Marx argues, because the material basis for the religion has not been destroyed. This view concludes that only when the material base of Christianity, industrial capitalism, is destroyed will Christianity whither away in all its forms.
At first, this critique of the Enlightenment project seems very strong. If Marx is correct in his materialist conception of history that all political ideas are the result of particular sets of social relations that comprise various modes of production, then he offers a compelling account of the history of ideas. But Marx is vague on what it means to be human. His assertion that humanity is defined by its consciousness of being a species-being is vague at best. The tension in his view is heightened when one observes that Marx actually goes so far as to imply that this connection may not be entirely material. And if it isn't entirely material, then cracks appear at the very foundation (strict materialism) for his social critique. It is difficult to see how a purely materialistic view of humanity can hold forth a teleological view of history.
And it is on precisely this point that Kant's conception excels. Kant's argument doesn't rest on a hidden relationship between individuals but on empirical observations. For Kant, even though free will may be a chimera, it is enough that human beings appear to have free will. The mere appearance of human action, for Kant, is sufficient basis to attempt the construction of universal laws that human actions appear to follow.
[This is an edited form of my answer to two essay questions from the final exam I took for Professor Robert Rethy's Late Modern Philosophy class at Xavier University in 2005. Professor Rethy wrote that my essay concerning Kant and Marx was brilliant so I thought that it might be worth sharing. The portions relating to Marx's critique of Bruno were a separate answer to the portions contrasting Kant and Marx. But I thought that it gave a very good look at what Marx was trying to say so I folded it into the body of the answer to the other question.]