Sandaihiho the Three Great Secret Dharmas (三大秘法)
Sandaihiho (the Three Great Secret Dharmas) comprises the fundamental dharmas in Buddhism by Nichiren and consists of Honmon no Honzon (the Object of Veneration of the Essential Teachings of the Lotus Sutra), Honmon no Kaidan (the Platform for the Receipt of the Precepts and Place of Practice of the Essential Teachings of the Lotus Sutra) and Honmon no Daimoku (the Sacred Title of the Essential Teachings of the Lotus Sutra). It has been described in "Hoon-sho," "Hokke-shuyo-sho," "Sandaihiho-sho" and so on.
Formally, it is called 'Hokke Honmon-no-Sandaihiho (法華本門の三大秘法).'
It means the Homon (dharma gate), which is secretly embedded within key sentences in the Hoke-kyo Sutra.
As opposed to Goko-han (五綱判) (Shukyo-no-Goka (宗教の五箇)), which focuses on the relative advantage of the sect as compared to other sects, Sandaihiho is called Shushi-no-Sanka (宗旨の三箇) and is generally understood as a principle of transcending and resolving all conflicts from the viewpoint of absolute mercy.
Each Hokke sect interprets it differently, but the following interpretations of the Nichiren sect and Nichiren Shohu sect are representative examples for both ends of the spectrum.
Interpretation of Sandaihiho by the Nichiren sect/Hokke sect (Nichiren lineage in general)
Honmon no Honzon': Honmon no Honzon is a Buddha, specifically Sakyamuni in Gaya Jodo (伽耶成道), who has recognized himself as Nyorai throughout the eternal past, which is written in "Juryo-bon" (a part of the sutra).
Honmon no Kaidan': The place where Daimoku (Namu Myohorenge-kyo) is recited in front of the Honzon (principal image) is known as the "dojo," a place for training (Sokuzedojo (即是道場)).
Honmon no Daimoku': Namu Myohorenge-kyo, which is The Three Thousand Realms Contained in One Mind of enlightenment by Sakyamuni.
According to the mainstream thinking (such as that of the Icchi-ha sect), these are regarded as general ideas in one's mind, and if one recites the Nichiren chant in front of the principal image--as determined by the Nichiren sect--the place will become 'Honmon no Kaidan.'
Interpretation of Sandaihiho in the Nichiren Shoshu sect
Honmon no Honzon (Nichiren Shoshu sect)': Hito-no-Honzon (human principal image) is Nichiren Daishonin (大聖人) and Ho-no-Honzon (principal image of dharma) is Namu Myohorenge-kyo of koto-no-ichinensanzen (事の一念三千), (the Three Thousand Realms Contained in One Mind).
(The Great Mandala includes both dharmas.)
Honmon no Kaidan': Koto-no-kaidan is a place where Honmon Kaidan Dai-Gohonzon (principal image) is enshrined, and Gi-no-kaidan is a place where Gohonzon stays.
Honmon no Daimoku': The Nichiren chant of belief (信の題目) is to believe Honmon Kaidan Dai-Gohonzon, and the Nichiren chant of practice (行の題目) is to recite Namu Myohorenge-kyo by oneself and recommend it to other people.
Among the Sandaihiho, the principal image is considered to be the supreme entity. Sandaihiho was created as the root of Dai-Gohonzon of Honmon no Kaidan, which was said to have appeared before the founder of the sect on October 12, 1279, and if one opens this it will become Rokudaihiho (the Six Great Secret Dharmas) of the principal images of human and dharma (Koto-no-kaidan and Gi-no-kaidan) and the Nichiren chants of belief and practice; but if one opens it more, it becomes all 84,000 Homon in Buddhism.
Ichidaihiho (the One Great Secret Dharma) means Honmon no Honzon. In other words it means Dai-Gohonzon, which includes all Sandaihiho. If it is opened, it becomes Sandaihiho and Rokudaihiho. When combined, they become Ichidaihiho.
(See Egihanmon-sho in Rokkan-sho (Six-volume Writings).)
Others
Kokuchu-kai (before the defeat in World War II), Nichiren Shohu and Soka Gakkai (during the post-war period from 1955 to 1965), Fuji Taiseki-ji Kensho-kai and others endeavored to finalize a proposition for a national kaidan (although Nichiren Shohu and Soka Gakkai eventually withdrew the proposition for a national kaidan a few years before the construction of Shohon-do). They are said to be rare examples in that they tried to interpret Sandaihiho around Kaidan.
Moreover, particularly after the great march of the Shakubuku (an evangelistic technique, in Japanese meaning "break and subdue") of Soka Gakkai, which was started in 1951, the three of the freedom of religion, nonintervention against civil affairs and the Juvenile Act have been given the slang expression Sandaihiho in order to show the shilly-shallying of public administrations such as the government, police and courts of law from both sides, specifically the victims of Shakubuku and the assailants (the devout believers). Especially, there is information that some experienced members in radical associations advise young members that 'even if your aggressive Shakubuku is in fact accused of the crimes such as threatening, arson, abduction and confinement for the first time, you will be exempted from prosecution as long as you are underage (this includes "suspension of prosecution" as a result of admitting crimes). This term is used in the same sense on both sides--victims and assailants--which is rarely seen among Buddhist sects of Nichiren lineage, because they usually use different terms and interpretations.