This paper provides keys for understanding the reasons why the notion of discernment (chi) occupied a prominent place in Kaiho Seiryô's writings. It begins by reminding Kaiho's career as a descendant of a warrior lineage, his Confucian education, the scholarly influence his father exercised on him, and his choice to leave definitively the capital Edo and settle at Kyoto after having spent several years traveling around the country and made his living as a lecturer. It then turns to the way Kaiho perceived social order as a natural order governed by a rationale (ri), and explains that discernment was the only faculty that could justify that warriors occupied a dominant position. It also describes the method Kaiho imagined for achieving real discernment, that is the ability to forget one's own interests, to enter into others' minds and determine objectively where the long-term interest of the society lies.