In 1065, as the adopted son of the late emperor Renzong, the new emperor Yingzong of the Northern Song dynasty (960–1127) was involved into an intense debate over how he should address his biological father, the Prince of Pu. This controversy which lasted for approximately 18 months was known as the “Puyi” debate. The Grand Councilors suggested Yingzong to designate the Prince of Pu as his “deceased father”. A large number of officials from other bureaus, including the Secretariats, Hanlin Academicians, Censors and Remonstrators, and ritual officials objected to this proposal. They insisted that Yingzong as the adopted son of Renzong should designate his biological father as his “deceased uncle”. Eventually, Yingzong was allowed to name his father as a “relative” under the permission of Empress dowager Cao, his adopted mother. Through an analysis of the opponents’ arguments against the grand councilors’ proposal, this article argues that Song scholar-officials since the 1050s were inclined to reveal their political stances through the interpretation of particular imperial rituals. From this point of view, this article provides a new explanation of the origin of the “Puyi” debate, and demonstrates how ritual learning merged with political agenda in the mid-Northern Song.