Ichinin Sanzen – three thousand realms in a single life moment refers to the doctrine expounded in the Lotus Sutra that each single moment of life encompasses all three thousand possible realms of existence.
Okay, not the easiest thing to grasp, but it's one of the most important things you will ever read in this lifetime, I assure you.
Literally, ichinen sanzen can be translated as “moment of existence” and “three thousand aspects.” This is to say that each moment of existence of all living beings (ichinen) is endowed with all three thousand realms of phenomena (sanzen). Ichinen means a moment of life. Ichi means “one” and signifies the one ultimate truth or the Middle Way of the Dharma nature. A single moment of existence encompasses all the elements that form a common mortal’s life, such as body and mind, and cause and effect. The term refers to all forms of existence. Sanzen includes every single phenomenon in the entire universe. This doctrine teaches that even the smallest bit of life possessed by any single entity is actually endowed with all phenomena of the three thousand different realms.
Nichiren Daishonin says in the Gosho, “The True Object of Worship”:
When
he finally revealed in the “Great Concentration and Insight” (Maka
Shikan) the way to perceive the true nature of life, he at the same time
used the “three thousand realms” as a way to understand it. This is the
ultimate truth of his teachings.
(Gosho, p. 645)
Thus, ichinen sanzen is the ultimate principle of Buddhism and the ultimate truth of the Lotus Sutra.
The Doctrine of Ichinen Sanzen
This doctrine was systematized by T’ien-t’ai using concepts such as the Ten Factors of Life revealed in the Theoretical Teaching of the Lotus Sutra (Shakumon), and the Mutual Possession of the Ten Worlds and the Three Realms of Existence, which were revealed in the Essential Teaching (Honmon). The doctrine of ichinen sanzen was expounded for the first time in Volume Five, Chapter Seven of T’ien-t’ai’s “Great Concentration and Insight” (Maka Shikan). In developing the theory of ichinen sanzen, T’ien-t’ai placed primary focus on the Ten Factors of Life which were preached in the Hoben (“Expedient Means”—2nd) Chapter of the Theoretical Teaching. He borrowed the doctrine of the Essential Teaching of the Lotus Sutra to clarify that a single entity of life possesses three thousand realms. Volume Five of the “Great Concentration and Insight” states:
At
each moment, life is endowed with the Ten Worlds. Concurrently, each of
the Ten Worlds is endowed with all the others. Therefore, an entity of
life actually possesses one hundred worlds. Each of these worlds
possesses, in turn, thirty realms. This means that in the one hundred
worlds there are three thousand realms. “Three thousand realms” might
also be read as “three thousand factors.” But the number is the same.
The only difference lies in the method of expansion. The three thousand
realms of existence are all possessed by a single entity of life. If
there is no life, that is the end of the matter. If however, there is
even the slightest bit of life, it contains all the three thousand
realms…. This is what we mean when we speak of the “region of the
unfathomable.”
(Quoted in “The True Object of Worship”; Gosho, p.644)
Each moment of a common mortal’s life contains all Ten Worlds. Each of these worlds, itself, possesses within it the Ten Worlds, making one hundred worlds. Each of these one hundred worlds possesses the ten factors of life, making one thousand factors of life. Each of these factors of life possesses the three realms of existence, which makes a total of three thousand realms of existence.
The relationship between ichinen (a single moment of existence) and sanzen (three thousand realms) is not temporal. In other words, a single moment of existence does not precede the appearance of the three thousand realms, nor do the three thousand realms precede a single moment of existence. Neither preconditions the other. Additionally, they are not two separate principles existing simultaneously. They are intrinsically one. “Endowed with,” in the above Gosho quote, is used to show this principle of oneness.
The Mutual Possession of the Ten Worlds, the Ten Factors of Life, and the Three Realms of Existence
T’ien-t’ai categorized the life conditions that could be manifested in a single moment of life into ten states. We call them the Ten Worlds. They are Hell, Hunger, Animality, Anger, Humanity, Rapture, Learning, Realization, Bodhisattva, and Buddhahood. Each of these worlds, from Hell to Buddhahood, is endowed with all the others. This is called the mutual possession of the Ten Worlds. The Daishonin tells us in the Gosho, “The Opening of the Eyes”:
The principle of Ichinen sanzen begins with an understanding of the mutual possession of the Ten Worlds or states of existence.
(Gosho, p.526)
Thus, the concept of ichinen sanzen was developed based on the Mutual Possession of the Ten Worlds. The doctrine of the Mutual Possession of the Ten Worlds was not expounded in the pre-Lotus Sutra teachings. This explains why the people of the two vehicles (Learning and Realization) were said to be unable to attain enlightenment.
The Ten Factors of Life is a doctrine that divides the true entity of all phenomena into ten aspects. The word “factors” (nyoze) indicates that all forms of phenomena, just as they are, express the true aspect of the Middle Way. The Hoben Chapter of the Lotus Sutra states:
The true entity of all phenomena can only be understood and shared between Buddhas. (Yui butsu yo butsu. Nai no ku-jin. Sho-ho jis-so.)
This reality consists of the appearance, nature, entity, power,
influence, inherent cause, relation, latent effect, manifest effect, and
their consistency from beginning to end. (Sho-i sho-ho. Nyoze so.
Nyoze sho. Nyoze tai. Nyoze riki. Nyoze sa. Nyoze in. Nyoze en. Nyoze
ka. Nyoze ho. Nyoze hon-mak-ku-kyo to.)
(Kaiketsu, p. 24)
Nyoze so is form, appearance or behavior that we can see. Nyoze sho is original nature or character. Nyoze tai is entity or substance. Nyoze riki is potential power or capacity. Nyoze sa is action influenced by potential power. Nyoze in is inherent cause or a direct cause that brings effect. Nyoze en is a relational or subordinate cause that supports an inherent cause. Nyoze ka is latent effect that results from inherent cause. Nyoze ho is a manifest effect that appears when a latent effect becomes manifest. Nyoze hon-mak-ku-kyo to illustrates that Nyoze so and Nyoze ho are ultimately equal.
The three factors of appearance, nature, and entity are the substance of all phenomena. The six factors of power, influence, inherent cause, relation, latent effect, and manifest effect are the functions of all phenomena. All things in this universe exist and occur in these ten ways.
Next, the Three Realms of Existence are: the realm of the Five Components, the Realm of Living Beings and the Realm of the Environment. These realms are categories of phenomena arising from the unity of causes and conditions and do not exist independently of each other. The Realm of the Five Components illustrates that the five components (form, perception, conception, volition, and consciousness) vary from person to person. The Realm of living beings refers to the truth that the lives of common mortals who are formed by the temporary union of the five components experience different worlds of the Ten Worlds. The Realm of the Environment illustrates that there are differences in the places where the common mortals of the Ten Worlds dwell.
