Susan Carey’s The Origin of Concepts explores the developmental and philosophical underpinnings of human conceptual thought. Carey critically examines the empiricist view that concepts arise solely from sensory experience, advocating instead for the existence of innate core cognition systems in infants—specifically for objects, number, agency, and cause. A major focus is distinguishing between continuous conceptual development based on these innate systems and discontinuous conceptual change, which requires unique human learning mechanisms like Quinian bootstrapping to create new, incommensurable concepts such as rational numbers, mass, and density. The work integrates evidence from infant psychology (like looking-time and search tasks) with arguments from philosophy (like dual-factor theories of content) to offer an extensive framework for how the human conceptual repertoire originates and transforms over time.