Theodor Adorno and Max Horkheimer collaborated on a book calledDialectic of Enlightenment. It is a central book in the history of the Frankfurt school version of critical theory, and worth thinking about.
The history of the idea of "Enlightenment" is significant in Germany. The 18th century is often called the Aufklarung, which is roughly translated as Enlightenment, but does not exactly have the same sense as the English Enlightenment of the same period. The Germans were very concerned about what counted as enlightenment, and there were a host of essays written in the late 18th century on the subject. Kant wrote one of the most famous, "What Is Enlightenment?" (see here for an introductory essay). His answer?
Enlightenment is man's release from his self-incurred tutelage. Tutelage is man's inability to make use of his understanding without direction from another. Self-incurred is this tutelage when its cause lies not in lack of reason but in lack of resolution and courage to use it without direction from another. Sapere aude! "Have courage to use your own reason!"- that is the motto of enlightenment.
This ideal of enlightenment remains an important one throughout German intellectual history, but Kant's answer is questioned by later thinkers. Adorno and Horkheimer like the idea that we are striving to use our own reason, but they think it is much more difficult to achieve than it seems. Kant seems to think that we need to free our minds from mysterious powers that hold it in tutelage. A&H see this as the hold of myth over our minds. The problem is this: as we are more successful in this project, we gradually move all knowledge into the realm of science. Myth is lost, science prevails, as we realize that our previous tendency to see things through myth was really a projection of ourselves onto the world outside of us (see Feuerbach for the first statement on this). We think we have banished myth.
The problem is that we have not banished myth at all. Science simply takes over some aspects of myth. It becomes as self-certain as myth was. It is impossible to question it from the outside, because when it comes to knowledge, there is no outside. Furthermore, science comes to hold an irrational belief in positivism, the idea that observation and positive evidence are all that is needed for the establishment of knowledge, and that knowledge can be founded on a very few, very general principles. In fact, science of this sort, reliant on logic, dehumanizes the world, reducing human meaning to a bit of calculation. Essentially, we give up our rationality, since we are all just the same kinds of calculable bits in the world of knowledge.
One thing that this form of science cannot do well is account for real conflict in society. In the attempt to homogenize everything under general principles, conflict is overlooked or rendered invisible. The goal of science is the domination of nature, but the result is that the more control we have, the further back we go in cultural terms. One goal of the Enlightenment, the domination of nature, has been realized. However, that domination also dominates us. The other goal, our own freedom from domination, must now commence.