Kenmitsu taisei (a hypothesis about Japanese medieval Buddhism) (顕密体制)
Kenmitsu taisei refers to a hypothesis about a medieval religious theory in Japan, which was proposed by Toshio KURODA, a historian. The theory was proposed under the title 'Development of Kenmitsu System in Medieval Japan' in the book "Medieval Nation and Religion in Japan" (1975) published by Iwanami Shoten, Publishers.
After WWII, medieval Buddhism studies in Japan were led by the theory that old Buddhism, Nanto rokushu (the six sects of Buddhism which flourished in ancient Nara) and Heian nishu (the two sects of Buddhism that flourished in the Heian period: the Tendai and Shingon sects), co-existed separately and exclusively with equal power.
As an alternative, however, KURODA proposed the "kenmitsu taisei" theory built on the term 'kenmitsu' (then, it referred to Buddhism as a whole) found in historical documents.
The kenmitsu taisei theory claims that the authentic religion in medieval Japan, in fact, was kenmitsu Buddhism, which had been integrated under the umbrella of Esoteric Buddhism after the Heian period, and eight old Buddhism sects did not co-exist but formed a competitive order built on the absolute and universal truth of Esoteric Buddhism while sharing as the common foundation the characteristics peculiar to Esoteric Buddhism: prayers for peace of souls and ritualistic faith. The theory continues that there existed the (kenmitsu) system during the medieval periods, whereby old Buddhism temples such as Enryaku-ji Temple established their status as authentic national religion by maintaining the above-mentioned competitive order and forging a bond of relationship with the ruling class in the nation.
This theory provided a springboard for a shift in views from the belief that medieval Buddhism in Japan was represented by Kamakura New Buddhism (new schools of Japanese Buddhism founded during the Kamakura period), the view prevailing after WWII, to the belief that old Buddhism was the mainstream of medieval Buddhism. Also, this theory provided a new perspective on Buddhism history studies because it discussed Buddhism in a broader framework of political and social history on the assumption of the presence of a state system build on kenmon taisei (the system by which governance was shared among "influential houses" or ruling elites), which was proposed by KURODA.