The Mental World: Beyond the Iceberg’s Tip. The physical world we perceive is merely a surface layer—a “tip of the iceberg”—compared to the immense and unseen mental world that lies beneath. This hidden mental realm, often likened to “dark matter,” forms the foundation of human social intelligence, enabling us to navigate the intricacies of social interactions despite its inherent invisibility [19, 621]. In dynamic and unpredictable social settings, the ability to interpret subtle signals, recognize social events, reconcile perspective misalignments, and infer complex mental states and their transitions presents profound challenges. These difficulties are further compounded by the intricate causal connections between the physical and mental worlds, as well as the reasoning chains that rely heavily on shared commonsense knowledge.