In his three books on evolution, Biology and Knowledge (B&K; Piaget, 1971), Behavior and Evolution (B&E; Piaget, 1978), and Adaptation and Intelligence (A&I; Piaget, 1980), Piaget describes what he regards as a nexus of related evolutionary problems expressed at different levels of generality. These include (a) how humans evolved the capacity for constructing logical-mathematical structures; (b) how these structures can so accurately describe the world; (c) how organic and cognitive regulations (functions) correspond; and the most general question (d) how behavior and morphology could have co-evolved.