Research on infants’ knowledge of objects, places, and number provides evidence for core cognitive systems that capture abstract, interconnected concepts and are early-emerging, present throughout life, innate, and supportive of learning. These systems also are ancient (they are shared by a wide range of other animals), sharply limited, unconscious, automatically activated, and dependent on our limited attentional resources. Here the author suggests that these properties collectively form a natural kind: a cognitive system with some of these properties will likely have all of them. Notably, a cognitive system shared by diverse, distantly related animals will gain a primordial blessing of abstraction: For example, the core place system will represent only the abstract geometric properties that apply to all the environments of the navigating animals that possess it, including terrestrial rats, flying birds, and aquatic fish. In the coming chapters, the author uses these arguments to propose three more systems of core knowledge.