What is the importance and meaning of Simon's conversation with the pig's head/beast in "Gift for the Darkness"?Fromabout two thirds into the...

Simon's trance and conversation with the Lord of the Flies
is the theme of the book - that the evil in the world lies within the heart of mankind,
not from without.  As early as chapter 5, Simon has a basic understanding, not yet fully
realized by him, that the source of evil on the island is not a beast or anything that
isn't human.  As the chapters progress then to chapter 8, "A Gift for the Darkness",
this understanding becomes clearer to Simon.  By the time Simon has this conversation
with the head of the pig, the self-proclaimed "Lord of the Flies", Simon knows
absolutely where the source of evil is.  That is why he isn't afraid to explore and
check out for himself the dead parachutist and that is why he tries to tell the others
what he knows but is killed before he can do so.  The Lord of the Flies told him that
darkness was in the hearts of the others on the island and that should have been a
warning to Simon that the darkness itself would prevent Simon from sharing that
information.  At this point in the story, the evil (darkness) is stronger than the
goodness and the rules of civilization that had kept the evil at bay
previously.