Kagaku (study of waka) (歌学)
Kagaku is a study that researches everything related to waka, such as its essence and mannerisms, the interpretation of old waka, ancient practices and history. Usually, a discussion of the essence of waka is called a karon (treatise on waka poetry) and the study of various knowledge concerning waka other than karon is called kagaku.
The origin of kagaku goes back to the eighth century, but at that time it was an imitation of the poetics of China.
Beginning with the kanajo (a preface written in Japanese script) to the Kokin wakashu (Collection of Japanese Poetry from Ancient and Modern Times), which was written in the mid-Heian period, Japanese karon began to expand as a field, and kagaku began to flourish; in keeping with karon, research into the Manyoshu (an eighth-century anthology of Japanese poems) began.
From the early to the mid-Kamakura period, many karon books discussing the true essence of waka were written, among which were FUJIWARA no Toshinari and FUJIWARA no Sadaie's "Yugen" and "Ushin," which later became the foundational texts for kagaku in later generations. Around the end of the Kamakura period, families of kagaku were established, whereby the Kyogoku family and Nijo family (Reizei family) were opposed to each other. Once the Muromachi period began, customs like Kokin denju (the secret transmission of a certain interpretation of the Kokin wakashu) arose, and more progress was made towards the stabilization and formalization of kagaku as a discipline. Karon in this period had already moved beyond its original narrow focus on poetry and began to include essays on art in general or essays that outlined an entire ideological system, and thereby came to have a deep influence on other art forms; Zeami, who perfected the art of Noh, commented that "Kagaku is the only type of learning a Noh actor really needs."
In the middle of the Edo period, Mosui TODA, Choryu SHIMOKOBE, Keichu and others criticized chusei kagaku (medieval poetics). Three main schools of thought arose--the group made up of KAMO no Mabuchi, Munetake TAYASU, and others, which took the Manyoshu as its model; the group that included KADA no Arimaro and Norinaga MOTOORI, which took the Shin kokin wakashu as its model; and the group whose adherents included Roan OZAWA and Kageki KAGAWA, which took the Kokin wakashu as its model--these groups vigorously studied the Manyoshu, the Kokin wakashu and the Shin kokin wakashu, a state of affairs that continued until the early Meiji period.
In the mid-Meiji period, Shiki MATSUOKA's theory of Shaseishugi (realism) first came out, and it shook the world of karon to its foundations. The kagaku of the Meiji period and thereafter was focused on studying ancient waka and old waka anthologies rather than on karon itself; as a result, remarkable progress has been made in research on the Manyoshu and the Kokin wakashu, in study of the history of waka and of karon, and in the bibliographic study of old waka anthologies.