Grendel is portrayed as the negative force in the epic of Beowulf and that is also apparent in the way he divides the world. He thinks the world can be divided into two which are:
1) Those things
which can be killed or murdered constitute one part.
2) Those
things which stop or put hurdles in the killing of things are the second part.
An interesting example of this is present in the epic in the
form of "Geats" who Grendel thinks are things to kill and also things
which stop the killing of the things :)