As populations and cities grew, the need grew for the establishment of rules of conduct within the newly organized societies. After the development of the Alphabet, these rules were written down along with the punishments that kept them enforced. The earliest known such codes existed in Babylon, India, and Palestine. Roman law was the first to distinguish between public law, in which the state is involved, and private law, concerning disputes between citizens. U.S. law was greatly influenced by the work of Sir William Blackstone, who stressed the natural rights of the individual.