How does Immanuel Kant define "enlightenment" and what is the signifance of his definition?

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:

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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.