The dog chasing his tail invokes the ouroboros, an ancient symbol of a snake eating its own tail. This image is usually interpreted to represent the inevitable and cyclical nature of transformation—particularly the cycle of birth, life, and death. In this instance, the dog serves as a metaphor for Brand’s quest for knowledge. The fact that the dog can’t catch its own tail implies that Brand’s search for the Unpardonable Sin, which supposedly lies in his own heart, has been similarly impossible, since he can never know for sure (nor prove to others) if he really has found it. Moreover, the Unpardonable Sin (as Brand sees it) is circular in the fact that searching for it necessarily entails committing it—which means that it can’t be objectively assessed. In searching for the Unpardonable Sin, then, Brand has become his own enemy, driving himself away from human connection and behaving against his own interests. Where the dog makes a lot of noise, Brand makes many assertions of his own sinfulness—but without presenting any evidence or referencing anything external to himself that could be used to evaluate his claims.