Mental models are simplified representations of how the world works that shape perception, reasoning, and decision-making, and having a diverse toolkit of models produces dramatically better judgment. Parrish draws on Charlie Munger's concept of a latticework of mental models, arguing that the most effective thinkers operate across disciplines rather than within a single framework. The article introduces twelve foundational models from inversion and second-order thinking to map-territory distinction and circle of competence, showing how to apply them to business decisions.