The whole John Donne meditation the title is referencing:
No man is an island,
Entire of itself;
Every man is a piece of the continent,
A part of the main.
If a clod be washed away by the sea,
Europe is the less,
As well as if a promontory were:
As well as if a manor of thy friend's
Or of thine own were.
Any man's death diminishes me,
Because I am involved in mankind.
And therefore never send to know for whom the bell tolls;
It tolls for thee
(had to memorize it in High School, and its one of my favorites. It was written over 400 years ago and has aged quite well.)
