<論説>鈴印の保管・運用と皇権

Abstract

本稿では、鈴印の所在が皇権の掌握者を示すという通説と、皇権の遂行主体の再検証を目的として、鈴印使用に関する権限を「保管権」「運用権」に峻別して個別に検討した。鈴印に関しては、奈良時代から内裏で保管され、少納言・主鈴のみが請進・出納業務を行うという原則が確認できた。特に内印は遷都を除いて内裏外に持ち出すことはなく、その保管権は天皇に集約されていた。一方、運用権は、天皇と太上天皇がともに持つ場合があり、天皇に一元化されず、皇権の遂行主体が二分するというこの矛盾は、両者の政治的対立の一因となった。このため、薬子の変を契機に、皇権の天皇への一元化が図られるが、律令文書行政の凌駕を意図する蔵人設置は、鈴印自体の効力低下をも招く事になった。さらに、鈴印形骸化のもう一つの契機は、皇位継承者不在の称徳の崩御である。群臣による皇太子決定は、鈴印奉上の形で鈴印運用へ群臣を介入させ、その限定性を崩壊させる端緒となった。

This study represents a reappraisal of both the nature of Imperial authority and conventional wisdom regarding the possession of the official imperial seals of office (Rei-in). This monograph analyzes how these seals were used and protected and the implications this has for the nature of sovereignity in ancient Japan. During the Nara era (710-84), the Rei-in was stored in the palace and only lesser ministers of state (shonagon 少納言 and shurei 主鈴) had the authority to take out the seals and allow them to be used. Save for times when the capital was being moved, these seals could not be removed from the palace. Nevertheless, both emperors (tenno 天皇) and retired emperors (dajo tenno 太上天皇) could use these seals. The resulting bifurcation of imperial authority represented a continuing source of political tension. Nevertheless, after the defeat of the retired emperor's forces in the Kusuko 薬子 rebellion in 810, the emperor came to monopolize use of these seals. Ultimately, however, with the destruction of the ritsuryo order and the creation of a private imperial secretariat, caused the Rei-in to lose its significance. The death of the tenno Shotoku 称徳 in 770, and the absence of a designated heir to the throne, proved instrumental in causing the Rei-in to decline in importance, as the ministers of state gained for the first time the power to use the imperial seal, which meant that it could no longer be exclusively used by emperors.