Answer: Lincoln said the best way for the living to honor the dead is to continue to fight. Their father, grandfather, uncle, brother, etc, gave their lives to end slavery. They have to fight to win the war because the outcome of the war is what they were all fighting for.
Step-by-step explanation:
Lincoln's primary purpose was to dedicate the cemetery of fallen soldiers. His secondary purpose was to convince listeners to dedicate themselves to preserving the nation.