<論説>平安貴族社会と「貴種」

Abstract

貴種は日本中世権門の上流階層の身分を表す概念であるが、その語は古代の史料からも見られる。古代史では貴種を天皇の血統と関連付けて、中世の貴種との関係は言及されなかった。本稿は、史料上の「貴種」の用例を検討し、その成立と転換の考察を通して、古代から中世への転換期における社会の変容の様相を捉える。まず、九世紀の文人貴族による文書から「貴種」が三位以上ないし公卿の子孫、ひいては王臣家の子弟を指すことを明らかにした。歴史学ではあまり使われなかった詩序を史料として活用し、貴族日記の記事を分析することで、持続的な公卿地位の継承なしに「貴種」と称される家柄の存在を一一世紀後半から確認した。同じ先祖を持つ門流から「貴種」の家とそうでない家が分岐する現象を通して、一一世紀中葉には貴族社会の変動に伴って「貴種」の家が成立し、家格の性格を帯びるようになった「貴種」が中世権門の身分へとつながった点を指摘した。

Kishu 貴種 (noble birth) is used as a term while discussing the class structure of Medieval Japan. This term is related to the theory of kenmon taisei (the system of governance by several powerful families) proposed by Toshio Kuroda. It is said that kishu is the primary social class for a group of leaders from powerful aristocratic families, and prescribed by the standard of an official rank. However, although Kuroda brought the word kishu from historical records in the medieval period, it is also found from 9th century documents. In the aspect of ancient Japanese history, kishu is considered as the word concerning the lineage of the Emperor. The relationship between ancient and medieval concepts of kishu has not been argued at all. Establishing a consistent understanding of kishu is important for a discussion of the turning point in Japanese history, a serious change from the ancient society to the medieval one. In this article, I clarify the meaning and the indicated target of kishu using examples of historical records during the Heian period, especially shijo(preface of poems) which was rarely used in historical researches, so that new findings on families and the family status in Japan's medieval age can be provided. The first appearance of kishu in historical documents is in the early 9th century. It is used by a scholar-nobleman who used to be a monjōshō (student of literary studies in the Imperial University), as a meaning of 'offsprings of 3rd court rank officers or higher.' It is determined that the word kishu came from literature and history books of ancient China, which were textbooks for monjōshōs. According to those examples, it is found that kishu was relevant to the blood of noblemen who had high court rank. It does not apply to the Imperial family. However, Sugawara no Michizane, a scholar-nobleman with a monjōshō career, was using the word kishu in a different way in the late 9th century document. He called a daughter of the Emperor as kishu, so that a member of the Imperial family was treated like offsprings of high rank noblemen. Each of 3rd court rank officers or higher was given his own domestic governing institution, and it was same for sons and daughters of the Emperor. Those families were called Ōshinkes, which were so powerful that they began to have influence over the appointment of monjōshōs in the early 9th century, when the word kishu first appeared. Therefore, considering the actual situation at that time, kishu indicated descendants of Ōshinkes as powerful families. After that, the word kishu did not appear until the middle of 11th century. It is remarkable that kishu is not shown during the Sekkan period. In the late 11th century, the first example of kishu was found froma diary of a nobleman, used with the word kaimon (family of the minister). Compared to the 9th century, kishu was focused on a certain family, not the personal court rank. Many examples of kishu in shijos of the 11th-12th centuries are found with words like families of ministers or court nobles. In other words, descendants from families of ministers or court nobles were called kishu. A family of ministers or court nobles is a group of people who have their ancestors of ministers or court nobles. If a member of that family is not in a position of court noble, he could still be called kishu. On the contrary, even though a person who does not belong to the family of kishu became a court noble of high rank, his family could not get the name of kishu. Unfortunately, it is difficult to find out when the family of kishu was established, because we lack historical records in the Sekkan period. However, if we search the last generation of court nobles in a family of kishu and the first person who could not reach the position of court nobles as an ancestor of a non-kishu family, they were people in the middle of 11th century. At that time, the meaning of the word kishu as a family status became clarified. It was because Fujiwara Sekkan family declined and found it hard to produce many court nobles. In contrast, members of other families obtained promotion to become court nobles. Therefore, the word kishu became limited to families around the Sekkan family. And there is some possibility that the concept of kishu as a family status was started to be made from 10th century, when offsprings of Fujiwara no Morosuke prospered. It is said that family status in the medieval Japan existed, such as kindachi (able to be court nobles) and shotaifu (under court nobles). Kishu was a different status from kindachi, and it became the name of the social class for powerful families of the Heian aristocracy.