A theory of the formal structure of commonsense concepts. In Conceptual Form , Sandeep Prasada develops a new and original approach to the study of commonsense concepts. He argues that lexically expressible concepts such as DOG possess a formal structure—a conceptual form—which provides perspectives for thinking, talking, and reasoning. These perspectives are not a property of the things the concept represents. Rather, they are “mental lenses,” or ways of thinking and talking. The conceptual form functions as a mental lens by providing instructions for how to think and talk about what the concept represents. The book is unique in its focus on the formal dimension of commonsense concepts, its original proposal for how the type-token distinction is realized within our conceptual systems, its proposal that the core of concepts involves the acquisition of principles, not facts and generalizations, and its detailed consideration of linguistic and experimental data in the formulation of the theory of conceptual form. Finally, this book provides a new perspective on classic questions concerning the atomicity and innateness of concepts. Even those who disagree with specific claims are likely to find the theoretical tools and distinctions introduced by the theory of conceptual form to be valuable in their investigation of concepts.