Eisai

Importing green tea

Eisai is also credited with the beginning of the tea tradition in Japan, by bringing green tea seeds from China, back from his second trip in 1191, and writing the book 喫茶養生記, Kissa Yōjōki (in English, Drinking Tea for Health). Legend says that he planted the seeds "in the garden of the Ishigamibo at Seburiyama in Hizen".

In addition to his book, Eisai also garnered attention from another act involving his tea; using it as treatment for shōgun Sanetomo. This is a record of his treatment from the Azuma Kagami:

The shōgun was taken a bit ill, and various attendants attempted to treat him. This was not so serious but was from overindulgence in wine the previous evening. The priest Yojo, who had come to perform incantations and learned the situation, brought a bowl of tea from his temple, saying it was good medicine. He also asked the attendants to give the shōgun a scroll of writings about the virtues of tea, and the shōgun was said to have been greatly pleased. Priest Yojo indicated he had written it recently during his breaks from meditation.

Eisai was more focused on the medicinal aspects than anything else, and the main reason for this was the common conception of the time that the world was in mappō, the Latter age of the Dharma, which was considered by many to be a time of decline. Eisai lived through an era of heavy fighting in Japan, so mappō played a big role in his promotion of tea, as he thought it was a cure for many ailments and hence would help people get through this perceived difficult time.

In Kissa Yōjōki, the beginning bulk of text after the prefaces concern the alignment of the five elements of Chinese science (earth, fire, water, wood, and metal) with five major organs (the liver, lungs, heart, spleen, and kidneys) and the respective five flavors that each major organ preferred (acidic, pungent, bitter, sweet, and salty). Eisai claimed that the standard Japanese fare of the time contained abundant amounts of each, except for the bitter flavor, which was the cause of the many heart diseases the Japanese suffered from. He asserted that his green tea was essential for providing the bitter flavor, and thereby keeping the heart healthy.

Promotion of Buddhism

During the Nara and Heian periods in Japan, Buddhism was used as a tool to unify the country. Eisai was a firm believer that it should be Zen Buddhism to aid the protection of the country. He identified previously established schools of Buddhism as responsible for contributing to Japan's struggles.

During this time, three major scriptures were used to promote this idea of a unified Buddhist Japan: the Lotus Sutra, Golden Light Sutra, and the Humane King Sutra (Ninnōkyō). Eisai's famous written piece, The Promotion of Zen for the Protection of the Country (興禅護国論, Kōzen gokokuron), was heavily influenced by the Humane King Sutra, which states, "The preservation of Buddhism is inextricably bound to the preservation of their own country". The Kōzen gokokuron was written with the intention to correct established schools of Buddhism by giving them examples of moral practice and to convince the Minamoto military rulers to support Zen Buddhism and a Zen government. The writing promotes the Zen ideals to bring Buddhism back to its morals and practices.

Eisai's writing depends heavily on the idea that Buddhism is critical for a functioning society. The Kōzen gokokuron is often regarded as nationalistic propaganda, and due to the compromises he made when working to install Zen Buddhism in Japan, people disregard the significance of the Kōzen gokokuron when reading it from a "pure" Zen perspective.