In Victor Hugo's "Les Miserables," the quote suggests that both diamonds and truths require a journey into darkness to be discovered. Just as diamonds are formed deep within the earth, hidden away from light, profound truths often lie buried within our thoughts and experiences. This metaphor emphasizes the idea that valuable insights and truths are not always visible on the surface and require introspection and exploration to be revealed.

The quote also implies that challenges and struggles can lead to enlightenment. It encourages readers to look beyond superficial appearances and to seek deeper understanding. By acknowledging that both beauty and truth are often concealed in darkness, Hugo invites us to confront our personal struggles and delve into the complexities of our minds to uncover the wisdom that lies beneath.