The quote "When you only have a hammer, everything looks like a nail" suggests that one's perspective is limited by the tools or approaches they have. In Jodi Picoult's "My Sister's Keeper," this idea manifests through the characters who, constrained by their experiences and beliefs, often resort to simplistic solutions for complex problems. Their one-dimensional viewpoints lead to conflict and misunderstanding within the family.

This phrase serves as a metaphor for how individuals may disregard other potential solutions when they rely too heavily on a specific method or perspective. In the context of the novel, it emphasizes the importance of broadening one's mindset to navigate the intricate emotional and ethical dilemmas faced by the characters, particularly in matters of health and family dynamics.