Honji suijaku

The term honji suijaku or honchi suijaku (本地垂迹) in Japanese religious terminology refers to a theory widely accepted until the Meiji period according to which Indian Buddhist deities choose to appear in Japan as native kami to more easily convert and save the Japanese. The theory states that some kami (but not all) are local manifestations (the suijaku (垂迹), literally, a "trace") of Buddhist deities (the honji (本地), literally, "original ground"). Thus, for example, the deity Amaterasu was considered a trace of Dainichi Nyorai (Great Sun Buddha).

According to the theory, the two elements form an indivisible whole called gongen, and in theory should have equal standing, but this was not always the case. In the early Nara period, for example, the original ground (honji) was considered more important and only later did the two come to be regarded as equals. During the late Kamakura period some theories proposed that the kami were the original deities and the buddhas their manifestations (see the Inverted honji suijaku section below).

Honji suijaku theory was never systematized but it was nonetheless very pervasive and very influential on Japanese religions. It is considered the keystone of the shinbutsu-shūgō (syncretism of Buddhist deities and Japanese kami) edifice. Honji suijaku has often been seen as similar to interpretatio Romana, a mode of comparison promoted in antiquity by scholars such as Tacitus who argued that barbarian gods were just the foreign manifestations of Roman or Greek deities.

The term honji suijaku itself is an example of the Japanese practice of Yojijukugo, a four-character combination of phrases which can be read literally or idiomatically.