He placed an introduction at the beginning of the first volume describing the overall concept, which holds that after the Fujiwara regime was formed, 'the general trends of the world' in Japan 'changed nine times' until it became an age of warriors, then 'changed five more times' before the Tokugawa regime came into existence, namely, 'the theory of the world changing nine times and then five times.'
第1巻の最初に総論を置き、日本における「天下の大勢」が藤原政権成立後、「九変」して武家の時代となり、さらに「五変」して徳川政権の成立を見たという全体の構想、すなわち｢天下九変五変説｣を述べる。