Ichinen sanzen (一念三千)
Ichinen sanzen is a kanpo (meditative training to reach enlightenment) and fundamental principle of the Tendai sect. It means that the three thousand realms are contained in one mind. It is said that ichinen sanzen was created by Chigi, who was a Tendai Daishi and the founder of Chinese Tendai sect.
Summary
Ichinen means momentary thoughts of ordinary people.
Sanzen (three thousand) indicates the development of hossu. It becomes one hundred realms because the ten realms share the other nine realms (Jikkaigogu, Mutual Containment of the Ten Realms), and since there are Junyoze (Buddhism Ten Factors of Life) in each of the hundred realms, it becomes senyoze (a thousand factors). Since senyoze exist in the three types of worlds: the five skandhas, kemyo, and kokudo; and therefore, there are three thousand. In other words, ten realms x ten realms x ten factors x three worlds = three thousand.
In the Tendai sect, ichinen sanzen suggest the uniform way of viewing the universe from the small to big; in a practical meaning, it indicates to view the spiritual realm of Buddhahood in one's own mind.
Establishment and background
The following is how this principle of ichinen sanzen came to be formed.
Although Chigi was the actual founder of the Tendai sect, there is another theory to regard Ryuju as the founder, Emon Zenji (Master of Zen Buddhism) as the secondary founder and Nangaku Eshi Zenji as the tertiary founder. It is said that the secondary founder Emon read the Madhyamaka-karika (Fundamental Verses on the Middle Way) written by Ryuju, and attained isshin sangan (threefold contemplation in a single mind). It is thought that ichinen sanzen is based on this isshin sangan.
Isshin sangan means to accept the three dogmas of "Ku (mind that is not bound by anything), Ke (or difference, a thought that things exits temporally) and Chu (or totality)" although the mind of an ordinary person keeps changing all the time.
According to the Tendai sect zensho (compendium) vol. 9, when Emon Zenji wanted to decide from whom he would learn Mahayana Buddhism, and asked in front of Daizo-kyo Sutra (the Tripitaka). Emon put his hands on his back, and decided that if he takes the sutra, he would choose Buddha, and if he takes the Ron (abhidharma), he would choose Bosatsu (Bodhisattva). However, he took Madhyamaka-karika (Fundamental Verses on the Middle Way) instead, so he decided to have Ryuju as his master. According to Madhyamaka-karika, Ryuju saw the line of 因縁所生法、我説即是空、亦名為仮名、亦是中道義, and entered Funihomon in those letters, attained kanpo (meditative training to reach enlightenment) in the isshin sangan (threefold contemplation in a single mind), and gave it to Nangaku Eshi.
Chigi developed Jikkaigogu on the premise of "isshin sangan," which lead to the thought of ichinen sanzen.
Chigi created a number of education and learning that had a great influence on the Buddhist region in the later generations, such as "Jikkai" (the Ten Realms), the view of the world. Ichinen sanzen is regarded as the ultimate principle of the Tendai sect among others. However, Chigi explained about ichinen sanzen only once in the first half of the volume 5 of his book "Makashikan" (Mahayana Practice of Cessation and Contemplation). Therefore, in the Buddhist Studies, Chigi is not regarded as the person who first promoted and developed the principle of ichinen sanzen.
It is thought that the reason why ichinen sanzen came to be regarded as the ultimate principle is because Tannen the Myoraku Daishi, who was the sixth generation from Chigi (ninth from Ryuju), interpreted that ichinen sanzen was Chigi's "final and ultimate theory"in "Shikan Bugyoden Guketsu Vol. Five" and preached people to follow it.
Also, Junyoze (Buddhism Ten Factors of Life), which is a component of the principle of ichinen sanzen, cannot be found in materials other than the original Sanskrit Text or the Lotus Sutra translated by Kumaraju. It is thought that junyoze was a free-translation by Kumaraju. For further details, refer to the section of Junyoze.
Succession and development
Although ichinen sanzen was originally created and developed by the Tendai sect, Nichiren succeeded the principle of ichinen sanzen and regarded it as the ultimate principle of the Buddhism. Nichiren discussed the practice of ichinen sanzen in Mappo (Age of the Final Dharma) in "Kanjin Honzon Sho" (Spiritual Contemplation and the Most Venerable One). He also said that ichinen sanzen would be complete by the essential teaching of the Lotus Sutra (Honmon), which is embodied into honzon (principal image of Buddha), and that the way to practice it is the sutra chanting of the Nichiren chant.
Especially, the line in "Kaimokumyo" which says "the teachings of ichinen sanzen is the true teaching of the Lotus Sutra, and written in the Juryobon" (Longevity Chapter) is famous. However, in the each school of the Nichiren sect, there is an argument over this line whether to regard Shakyamuni or Nichiren as the Honbutsu (Primordial Buddha).
Consequently, it is the schools of the Nichiren sect rather than the Tendai sect which currently promote ichinen sanzen as the ultimate principle of the Buddhism. Especially Nichiren Shoshu and other related religious communities often use the word ichinen sanzen.