The evolution of cognition. 1990.

With cultural evolution, new processes of thought appear. Abstraction is universal, but rationalization first appeared in ancient Greece, theorization in Renaissance Italy, and model building in twentieth-century Europe. These processes employ the methods of metaphor, metalingual definition, algorithm, and control, respectively. The intellectual and practical achievements of populations guided by the several processes and exploiting the different mechanisms differ so greatly as to warrant separation into cultural ranks. The fourth rank is not completely formed, while regions of the world and parts of every population continue to operate by the processes of earlier ranks.