Determination is something I would say
Well beowulf was an epic peom so there is no first hand source to tell you why. It was a story that was passed down from generation to generation.
Answer:
The tone of the story "roll of thunder, hear my cry" is mostly angry buuuuuuuuuuuuut at this point of the story I believe that it is serious!
I would say with naturalism or scientology