History of Ninjutsu: Mumon no Ikkan

無門の一関 Mumon no Ikkan (Page 162-163) from the book 忍びと忍術 Shinobi to Ninjutsu by 山口正之 Masayuki Yamaguchi

Mumon no Ikkan

In the two volumes of the “Shōnin-ki” written three centuries ago, the final three volumes are the so-called Okimitsuden, and in its first, it teacheth the secret transmission of Mumon no Ikkan. To state its outline, first:

“The heart difficult to enlighten is the heart of man. If one would have it spoken of, yet take heed and hide it deeply, so first speak of other matters, and draw it forth, and allure it with profit (hikitsukeru) that is best. Seek not the tip of words hastily. Press on with utmost pursuit. With single-minded intent—”

It saith thus. One must grasp the subtleties of the human heart and act accordingly; if one cutteth straight to the fore, the other groweth all the more wary, closeth the lid of his heart, and betaketh himself to silence.

Thus, turn the topic aside, direct the talk to an unrelated quarter, and fish with profit to make the other speak. Catch skilfully the tip of his words, pursue cunningly, and contrive to make him open his mouth.

It also stateth,

“Hiding a thing is the place where suspicion ariseth. Here set thy heart, and inquire gently and unhurriedly”—

thus teaching the way to deal with silence.

For such is the reason,

“When a man questioneth thee, receive it lightly and speak things unthought-of to see the other’s manner. From of old, the adage ‘In questioning one falleth not, but leaketh in talk’ is a famous saying. There, let him speak his fill of matters akin to what thou wouldst hear. Raise too great a stir, and thou shalt be disliked”—

thus expounding the essentials of the art of question and answer. Again,

“To speak principles unfit for one’s station, or clever things, is surely to be deemed taught from without. Principles not issuing from oneself will not work freely in application when the matter changeth.”

Thus it pierceth the folly of borrowed wisdom, that is, the importation of outer knowledge. Wherefore the essential way of the shinobi is,

“When one’s own principles are insufficient yet seeketh to measure another, one is surely exposed, and contrariwise measured by the other. Thus, only enrich one’s own heart, set profit full to the brim, and if there be a thin spot in the foe, boldly seek it forth.”

Here, it saith, one may attain the truth that breaketh through “Mumon no Ikkan.”

In the shinobi uta,

　おのずから利は有明の物なれば
　Onozukara ri wa ariake no mono nareba
　Of itself profit is the thing of the lingering dawn,

　　　ひらく扉に月ぞさし入る
　　　Hiraku tobiro ni tsuki zo sashi iru
　　　Into the opened door the moon doth enter.

A famous verse worthy of savoring.

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Notes

• 奥秘伝 (Okimitsuden): The innermost secret transmissions, referring to esoteric doctrines reserved for advanced initiates in ninja lore.
• 正忍記 (Shōnin-ki): A historical ninja manual attributed to the sixteenth century, detailing espionage and interrogation techniques; the text here likely alludes to a variant or related work.
• 無門の一関 (Mumon no Ikkan): Literally “One Barrier of No-Gate,” a metaphorical checkpoint in ninja training symbolizing the impenetrable human psyche, akin to a koan in Zen for breaking through guarded minds.
• 利をおごらす (ri o ogorasu): Archaic for “to lure with advantage or bait,” implying enticement through greed or self-interest; possible alternate reading as “to flaunt profit” in deceptive contexts.
• 言葉のはしばし (kotoba no hashikashi): The “tip” or “edge” of words, denoting fleeting hints or slips in speech that reveal hidden thoughts.
• 一意訳ー (itti yaku—): Appears truncated; likely “one intent, resolute” or “single-minded pursuit,” emphasizing unwavering focus in interrogation.
• 入れ智恵 (ire chie): “Inserted wisdom,” denoting external advice foisted upon one, contrasting innate intuition.
• 忍歌 (shinobi uta): Poetic verses in ninja tradition encapsulating tactical wisdom; this one evokes natural revelation through opportunistic openings.
• 有明の物 (ariake no mono): “Thing of the lingering dawn,” metaphor for something transient yet illuminating, like faint light revealing paths.

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