In "The Blue Sword," Robin McKinley explores the idea of transformation and the pressures to conform to a predetermined role. The metaphor of a grain of sand entering an oyster's shell symbolizes unexpected change and the expectation that one must adapt to such circumstances. The example raises important questions about identity and the notion of choice in the face of transformation.

The text further posits a thought-provoking scenario where the grain, instead of embracing its fate as a pearl, wishes to return to its previous existence in the ocean. This brings attention to the often-overlooked desire for autonomy and the right to remain unchanged, challenging the assumption that all change is beneficial or desired. McKinley beautifully captures the tension between potential and personal agency.