Kant believed that we only see the appearance of things (phenomena). We don’t see things-in-themselves (noumena). If we did see noumena, we would automatically choose the correct moral or logical option.
Since we only see the appearance of things, we are forced to make a choice. To make the correct choice, we cannot rely solely on the appearance of things; we must also use reason. If our reasoning brings us to the conclusion that 2=2=4, then we can choose that this is true in the material world as well.
The same concept goes for moral and social decisions. We must choose the correct option if it agrees with our individual reason. It is our moral obligation to do so. In other words, we must make a decision as if it adheres to a universal law. Kant called this duty of decision the “categorical imperative.” In order to make these decisions, we have to use reason and this requires that we think for ourselves. We cannot rely solely on our sense perceptions just as we cannot rely solely on what others have told us. For example, if you live in a society that endorses oppression or hate, you have the moral responsibility to be brave enough to use your individual reasoning to decide this is wrong. And you must act according to that reason.
In his essay, “Answering the Question: What is Enlightenment?” Kant said the Enlightenment was:
Mankind’s final coming of age, the emancipation of the human consciousness from an immature state of ignorance and error.
In Kant’s context, an individual becomes enlightened when he/she has the courage to act and think without the guidance of another. If an overall social enlightenment occurs, it is because the world has individually and collectively reached an era in history when they begin to think for themselves. Kant notes that the majority would probably continue to conform: too scared to think for themselves.
Enlightened individuals must not be restricted by thoughts of previous generations. Enlightenment entails progress. Only an individual who is courageous enough to think and reason for her/himself is able to make the best dutiful decision when faced with any choice: a categorical imperative.
This is significant for many reasons. One is that this established the idea that reasoned, individual thought is necessary to make moral decisions and it is also necessary when challening authority figures or public opinion. Kant established that the enlightened person must be courageous. This is also significant in that an enlightened ruler must be courageous enough to allow free thought and speech. These are the keys to an enlightened society.