how does chapter 12 of beowulf potray grendels personality and motives?

Through their battle, Beowulf introduces Grendel to the philosophy of empiricism. By forcing Grendel to accept the reality of the wall, he leads the monster to admit a reality external to himself. By cracking the monster’s head against the wall, Beowulf forces Grendel to face something he did not create in his own solipsistic existence.

Of note is the fact that Grendel’s painful lesson in empiricism leads him to create his first poem. Grendel has become a kind of Shaper himself, creating the reality of the wall for himself as he is pushed into admitting its existence. In one sense, Grendel has come full circle: his universe began as a solipsistic fancy of his own mind, and now is reduced to only that which he can experience firsthand. Conversely, Grendel now believes in a world outside himself, which does not so much create as recognize. Gone still is the Shaper’s false overlay on reality; Grendel is back where he started, for even now that he has recognized his experiences as valid input about the universe, he is about to end all experience as he bleeds to death in his dark cavern home.