Cho Ik(趙翼) regarded Book of Documents(書經) as a textbook for politics, especially for kings. So his study of Book of Documents was focused on the principles and methodologies of governing the state which were done by governors of Three Dynasties(三代). Cho Ik published a book contained the result of his research of Book of Documents, named Seo-gyeong Cheonseol (書經淺說). In Seo-gyeong Cheonseol , Cho Ik emphasized Lordly Virtue(君德), Bureaucratic Recruitment(用人), and Security of the people(安民) as principles of governing the state. Cho Ik thought that Lordly Virtue was the precondition of Bureaucratic recruitment and Security of the people, so he presented the cultivating Lordly Virtue as the most important thing which kings had to do. Cho Ik emphasized the importance of Bureaucratic Recruitment, because he thought that a king could not embody his virtue in governing the state without government officials. Cho Ik presented that moral nature and scholarship of Confucian classics(經學) must be the standards for choice of government officials. And he also asserted that if a king charged a government official with a certain task, the king had to entrust him with full power and not to interfere with his own personal opinion. Cho Ik said that Security of the people is the most important purpose of governing the state. He thought that the first step of Security of the people was economic enrichment and the last step was cultivating virtue of the people. So he emphasized the economic security of the people as the first task of national administration. But he also said that if the virtue of the people were not cultivated, the economic security could not be continued. And he presented education and administration of punishment as the methods of cultivating virtue of the people .