How is "darkness" used as a symbol in Heart of Darkness?

According to most scholars, the use of darkness in Heart
of Darkness represents the inherent evil (or dark side) in humanity.  It is also linked
to colonization, especially when involving the exploitation of people and natural
resources.

Throughout the novel, Conrad shows the reader
that appearances can be deceptive.  Our first view of this is the map of uncharted
Africa.  Marlow is able to see that the continent, when drawn, is for the most part
unknown.  As the result, it appears white on the map.  Through exploration,
colonization, and exploitation, the rest of the continent will be charted and filled in,
which will cause Africa to appear dark.  This is in direct contrast to the perception
that exploration brings "light" to a region.  Here, Conrad is trying to illustrate the
negative ramifications of colonization.

Conrad also uses
light and dark to tell us more about the inner state of specific characters.  Kurtz, a
Caucasian man, has white skin, but also has the darkest and most depraved soul in the
novel.  In addition to this, the reader discovers through Marlow that the African
natives are truly noble individuals.

Finally, Conrad closes
with the idea that darkness is not strickly limited to a continent.  Darkness of
humanity can appear anywhere.  Just like Kurtz, darkness can infect the soul of any
person.  In the closing of the novel, Marlow describes how some parts of England, even
with its civility and enlightenment, are just as "dark" as other places on the
globe.