In Margaret Atwood's "Stone Mattress: Nine Tales," the author explores the complexities and hidden depths of human nature and relationships. The phrase "Even guppies have their opacities" suggests that even seemingly simple or innocent beings possess their own mysteries and darker elements. This reflects Atwood's broader themes, indicating that appearances can be deceiving and that everyone harbors intricacies not immediately visible to others.

The short stories in the collection delve into various characters and situations, unveiling the latent realities that lie beneath the surface. Atwood's use of metaphor highlights the idea that understanding individuals requires digging deeper, as everyone, regardless of their outward demeanor, has their struggles and secrets. This portrayal encourages readers to consider the nuanced layers of existence that exist within all beings, prompting a more empathetic view of others.