Here's why:
* Dr. Jekyll represents the classical mind: He is a respected scientist, upholds Victorian morality, and strives for order and control. He embodies reason and logic.
* Mr. Hyde represents the Romantic mind: He is impulsive, driven by primal desires, and embraces the dark and taboo. He embodies passion, freedom, and the expression of the unconscious.
The novel explores the internal struggle within Jekyll as he grapples with the suppressed, darker aspects of his personality. He seeks to control his "evil" side but ultimately succumbs to its allure, demonstrating the powerful tension between restraint and liberation.
Furthermore, the novel's themes of duality, good vs. evil, and the power of the subconscious align with the Romantic movement's emphasis on the individual, emotion, and the exploration of the darker aspects of human nature.
While Stevenson's work predates the full emergence of Romanticism, it reflects the shifting intellectual landscape of the late Victorian era, which saw a growing interest in psychology, the unconscious, and the complexities of human nature – all key elements of the Romantic movement.