The Auxiliary まじ: Archaic "Mustn't" Surviving in Modern Set Phrases

The auxiliary まじ is the classical negative counterpart of べし, with senses such as "should not, cannot, surely not." In modern Japanese, it survives almost entirely as the frozen attributive form ～まじき in fixed phrases.¹ A serious reader meets it in editorials, formal denunciation, and fiction, so recognizing it matters far more than producing it.²

Overview

まじ conjugates as an adjective-type auxiliary (助動詞シク活用型). It negates the entire range of meanings carried by べし.¹ Where べし says "should, will, must," まじ says the opposite across the same set of senses.³¹

Almost none of the full classical paradigm lives on. What a modern reader actually encounters is the 連体形 (attributive form) ～まじき, locked into a small set of fixed phrases. There is also one terminal-form survival kept alive as a slogan.²⁴

まじ as the negative twin of べし

The cleanest way to hold まじ in memory is as the negative member of a pair. べし is the affirmative auxiliary (助動詞ク活用型); まじ is its negative (助動詞シク活用型).³¹ The classical auxiliary that gives modern Japanese its "should/must" sense, べき, is the affirmative twin of the form taught here.

The pairing is not just semantic. Both auxiliaries attach in the same way, which is the structural signal that they belong together. Each attaches to the 終止形 (terminal form) of a conjugating word. For ラ変-type words, each attaches instead to the 連体形 (attributive form).¹³

The senses mirror each other point for point. べし carries 推量・意志・可能・適当・当然・命令: conjecture, volition, potential, propriety, obligation, and command.³ まじ negates that whole set.¹⁵

The four dictionary senses of まじ

The 学研全訳古語辞典 collapses まじ into four numbered senses, each printed with a modern-Japanese gloss: ① 〔打消の推量〕 "(surely) will not, must not be the case" (…まい); ② 〔不可能の推量〕 "does not seem possible to"; ③ 〔不適当な事態〕 "ought not, had better not"; ④ 〔打消の意志〕 "have no intention of, will never."¹ A pedagogical breakdown adds 禁止 ("must not") and 打消当然 ("has no reason to") as separate labels. These are sub-readings of the same four-way core.⁵

The classical paradigm spreads these senses across many conjugated forms. That full table, including the gnomic readings and the precise ラ変 attachment rules, belongs to a study of classical Japanese grammar and is out of scope here. For the modern survivals, only the 連体形 まじき matters.¹⁵

A few classical examples show the spread of senses behind the modern fossil. The negative-conjecture sense ①:

かの国人くにびと、聞きき知しるまじく思おもほえたれども¹
"Though it seemed those people of that country surely would not understand it."

The impropriety sense ③, the one that feeds あるまじき:

妻めといふものこそ男をのこの持もつまじきものなれ¹
"A wife is the very thing a man ought not to keep."

And the negative-volition sense ④:

わが身みは女をうななりとも、敵かたきの手てにはかかるまじ¹
"Though I am a woman, I will never fall into enemy hands."

Modern Japanese keeps べき as the live 連体形 of べし. In exact parallel, it keeps まじき as the live 連体形 of まじ. Both are fossilized attributive forms of an otherwise dead paradigm.

What survives into modern Japanese

Almost nothing of the full paradigm survives in living use. With rare exception, a modern reader meets the 連体形 ～まじき in fixed phrases.² The auxiliary "has been replaced almost entirely by まい" in contemporary Japanese and "survives primarily in formal written contexts."²

The register is 文語 (literary), formal, written, and characteristically condemnatory. You see it in editorials, formal denunciation, legalistic prose, and fiction.²⁶ One terminal-form survival exists as a fixed slogan rather than a productive form, treated below.⁴

Form: the frozen 連体形 ～まじき

Attachment and the にあるまじき pattern

Classically, まじ attaches to the 終止形 of a conjugating word. For ラ変-type words and カリ-form adjectives, it attaches to the 連体形 instead.¹ The existential verb あり is ラ変, so まじ attaches to its 連体形 ある, producing あるまじき.⁷ This is why ある is the high-frequency stem behind the modern survivals.

The productive modern frame is Noun に + ある + まじき + Noun. A variant is Noun として + ある + まじき + Noun.²⁶ In デジタル大辞泉, あるまじき is itself registered as a 連語 (compound), the 連体形 of あり plus まじ.⁷

Only one form of the paradigm is needed here

The auxiliary conjugates as an adjective (形容詞型 / シク活用型) with full and カリ rows. Its 連体形 is まじき, its 已然形 is まじけれ, and it has no 命令形.¹⁵ For everything a modern reader encounters, only the 連体形 まじき is in play. The rest of the table is classical grammar.

The set collocations a reader actually meets

These are fixed phrases, not a live productive conjugation. Treat the list as lexicalized.²

あるまじき行為 means "conduct that should not be, outrageous conduct." あるまじき is the dictionary headword, glossed "あってはならない。不都合である。とんでもない。" (must not be, improper, outrageous).⁷

～にあるまじき means "unbecoming of, unworthy of." The dictionary's own internal example is 「指導者に―振る舞い」, "behavior unbecoming of a leader."⁷ The role-noun slot is open within this fixed frame. Fills such as 教師にあるまじき or 学生にあるまじき行為 are formed on the same template, rather than quoted as set phrases in their own right.²⁶

The role noun is a template slot, not a free invention

The verbatim dictionary example is 「指導者に―振る舞い」.⁷ You can swap the role noun (指導者, 教師, 学生, 教育者) into the attested にあるまじき frame, but the frame itself is fixed. The opening slot is for a role or status noun whose duties the conduct betrays. Do not treat ～まじき as freely productive beyond it.²

許すまじき means "unforgivable, not to be permitted," as in the condemnatory frame 許すまじき + Noun.⁶ 言うまじき(こと) means "words that ought not be spoken." It uses the same ～まじき + Noun frame.¹²

The proverb すまじきものは宮仕え means "serving others is something one would rather not do, if one can avoid it."⁸ The 故事ことわざ辞典 etymology states this explicitly: すまじき is the 終止形 of the サ変 verb す (為) plus the 連体形 まじき of まじ.⁸

A constructed instance of the にあるまじき frame, with the role noun filled into the dictionary template:

教育者きょういくしゃにあるまじき行為こういだ。
"It is conduct utterly unbecoming of an educator."

The proverb itself, sourced verbatim:

すまじきものは宮仕みやづかえ⁸
"The thing one ought not do is service to others."

One terminal-form survival is the bare 終止形 まじ kept alive as a slogan. The anti-nuclear song 「原爆を許すまじ」 ("We Must Not Forgive the Atomic Bomb") was composed in 1954 by 木下航二 after the 第五福竜丸 (Lucky Dragon) crew was irradiated in a Bikini Atoll test. It spread through the うたごえ運動 and was sung at the 1955 第1回原水爆禁止世界大会.⁴ It is the best-known modern survival of the terminal form:

原爆げんばくを許ゆるすまじ⁴
"We must not forgive the atomic bomb."

Nuance and usage contexts

The two readings: "unbecoming of" vs "must not / surely not"

The fixed phrases split into two readings. Each traces back to a sense of まじ and, through it, to a sense of べし.

The moral or role-impropriety reading (あるまじき, ～にあるまじき) means "unbecoming of, unworthy of, not proper for." This is the 不適当 (impropriety) sense of まじ.¹ It is a moral or social judgment. It is explicitly distinct from denying that something is logically possible (はずがない).² The dictionary gloss "あってはならない。不都合である。とんでもない。" sits here.⁷ As a twin relationship, this reading negates べし's 当然・適当, what one ought to do.³

The prohibition or negative-conjecture reading (許すまじき, 許すまじ) means "must not be permitted, cannot be forgiven." It draws on the 禁止 (must-not) and 打消推量 (surely-not) senses of まじ.¹⁶ In the song title, the terminal 許すまじ is a forceful negative-volition declaration: "we will not, we must not forgive."⁴ This reading negates べし's 命令・当然, what one must do.³¹

Register: where まじき belongs and where it does not

まじき belongs to editorials and formal denunciation, legal and formal prose, fiction and literary writing, and fixed phrases, proverbs, and slogans.²⁶ It does not belong to casual or conversational speech. Both JLPT references mark ～まじき as formal and literary, met in fixed phrases within written or literary Japanese.²⁶

For everyday meaning, a speaker reaches for living patterns, not まじき. Prohibition and obligation use してはいけない・するな・べきではない (and, for positive obligation, ～なければならない). Negative conjecture uses はずがない・ないだろう.¹ These modern glosses are exactly the ones the 古語辞典 supplies for まじ's senses, which is why they map so cleanly.¹

Good to know

Etymology: ましじ → まじ → まい

The form began as ましじ in the Nara period. It became まじ in the Heian period, then gave rise to modern まい in the Edo period.⁹ In contemporary Japanese, the auxiliary "has been replaced almost entirely by まい."²

The 連体形 まじき is the older attributive form that outlived the rest of the paradigm. The modern survivals (あるまじき, 許すまじき, すまじきものは…) are all 連体形. Meanwhile, the living function of the auxiliary moved to まい.²⁸

Knowing that まじ is the ancestor of まい reframes the fixed phrases. あるまじき is not an isolated idiom. It is the last 連体形 of a once-complete negative-of-べし paradigm.⁹²

～まじき vs ～べからず

Both forms negate べし, and a reader of formal Japanese meets both. It helps to keep them apart. べからず is the 連語 of べし (未然形) plus ず, glossed "（文末に用いて）禁止を表す。…してはいけない。…するな。" (used at sentence end to express prohibition).¹⁰

べからず is the more productive survival. It appears in live prohibition signage and notices, as in デジタル大辞泉's own example 展示品に手を触れるべからず ("Do not touch the exhibits").¹⁰ The signage pattern 〜べからず is recognizable to any modern reader. ～まじき is more lexicalized. It is confined to the handful of frozen 連体形 collocations above rather than freely generated.²

The two also occupy different slots. べからず closes a sentence (terminal, prohibition), while まじき modifies a following noun (attributive).¹⁰² Reaching for one where the other belongs is a mistake. They are not interchangeable.

The modern equivalents you would actually use

To express the meaning with living grammar, map each sense of まじ onto a modern pattern. Prohibition or "must not" uses してはいけない・するな, the same gloss the 古語辞典 gives for まじ's 禁止 and 不適当 senses.¹ Obligation-negation or "ought not" uses べきではない, the same territory as the modern ～ないほうがいい "you shouldn't" advice.⁵

Negative conjecture or "surely won't" uses ないだろう・はずがない, the 学研 gloss for sense ①.¹ These living patterns are what a learner should use to produce the meaning. まじき is for recognition only.

Pitfall: まじき is read, not produced

The tempting error is to coin new ～まじき phrases by analogy, for example 食べるまじきもの for "food one mustn't eat." That form is wrong. The natural modern phrasing is plain:

食たべてはいけないもの¹
"Food one must not eat."

～まじき is a lexicalized 文語 survival. Today, it is productive only within the fixed collocations and the にあるまじき / としてあるまじき role frame. Outside the handful of attested phrases, it reads as wrong or archaic-affected. The N1 task is to recognize まじき in reading and formal text, not to generate it.²⁶

A mnemonic ties it to the affirmative twin: まじき is "the べき that says no." If べき is "should, ought," まじき is its mirror: "should-not, unbecoming." The shared 連体形 survival and identical attachment (終止形, with 連体形 for ラ変) make the pairing easy to remember.¹³

See also

• The Classical Auxiliary べき: Should/Must (Modern Use)
• N1 Set Phrases Reference: A Glossed Catalog of Advanced Japanese Grammar
• JLPT N1 Grammar Checklist: The Curated List
• The Japanese Imperative Form (命令形): Plain Commands and Prohibitions

References

Footnotes

1. 学研全訳古語辞典『まじ』 (Weblio 古語辞典). https://kobun.weblio.jp/content/まじ ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰ ↩²¹ ↩²² ↩²³

2. まじき, Bunpro. https://bunpro.jp/grammar_points/まじき ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹

3. 学研全訳古語辞典『べし』 (Weblio 古語辞典). https://kobun.weblio.jp/content/べし ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷

4. 木下航二, Wikipedia (日本語). https://ja.wikipedia.org/wiki/木下航二 ↩ ↩² ↩³ ↩⁴ ↩⁵

5. 「まじ」, 古文の文法 (kotenbunpou.com). https://www.kotenbunpou.com/助動詞/まじ/ ↩ ↩² ↩³ ↩⁴ ↩⁵

6. まじき (majiki) Meaning, JLPT Sensei. https://jlptsensei.com/learn-japanese-grammar/まじき-majiki-meaning/ ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸

7. デジタル大辞泉「ある‐まじき【有るまじき】」 (Weblio). https://www.weblio.jp/content/あるまじき ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶

8. 故事ことわざ辞典「すまじきものは宮仕え」. https://kotowaza-dictionary.jp/k0354/ ↩ ↩² ↩³ ↩⁴

9. classicaljapanese.wordpress.com, "～まじ". https://classicaljapanese.wordpress.com/2015/03/18/maji/ ↩ ↩²

10. デジタル大辞泉「べからず」 (Weblio). https://www.weblio.jp/content/べからず ↩ ↩² ↩³