Arai Hakuseki's Kishinron is famous as a book which argued demon's reality and collected many Ghost story. And Kishinron is estimated low as "imperfect soul study" or as "Zhu Xi 朱熹's demon theory was copied". A conventional study pays attention to only demon's reality and doesn't grasp Hakuseki's insistence. For example, why did he criticize Buddhism in Kishinron? I would like to define the reason that he criticized Buddhism clearly.Hakuseki denied metempsychosis of Buddhism. He admited that a person is born from his parents and a soul and a body are formed by his parents.When metempsychosis is admitted, a soul will exist without his parents. This way of thinking lowers the value of his parents. The idea of metempsychosis cuts the connection of a person and his parents off.Hakuseki emphasized the worship of ancestor. Because a person knows importance of the family through bowing to his ancestor. Hakuseki tried to made people realize the connection with their parents and their ancestor through emphasized demon's reality.