Political science draws upon the fields of economics, law, sociology, history, anthropology, public administration, public policy, national politics, international relations, comparative politics, psychology, political organization, and political theory. Although it was codified in the 19th century, when all the social sciences were established, the study of political science has ancient roots that can be traced back to the works of Chanakya, Plato and Aristotle which were written nearly 2,500 years ago. Political science is commonly divided into distinct sub-disciplines which together constitute the field: