In Saul Bellow's novel "Herzog," the interplay of sentiment and brutality is a central theme, suggesting that human emotions and harsh realities are inseparable. The quote evokes the idea that these contrasting elements coexist in life, similar to how fossils and oil are found together in nature. This relationship reflects the complexities of human experiences, where tenderness often exists alongside harshness.

Bellow's exploration of this duality highlights the struggles of the protagonist, Moses Herzog, as he navigates personal turmoil and existential questions. The inherent tension between emotional depth and life's brutalities shapes his understanding of the world, illustrating that genuine feelings cannot be fully appreciated without acknowledging the more painful aspects of existence.