“〜de wa arumai shi”: It's Not As If 〜 (so…) [JLPT N1]

Content by NTJ Kuma · Nihongo to Japan editorial team · Updated July 27, 2026

「子供ではあるまいし、自分で決めなさい」 — using ‘it's not as if 〜' to criticize or point out that someone's behavior is inappropriate.

「子供ではあるまいし、自分で決めなさい」 — you're not a child, so be reasonable

Reasoning with a touch of reproach, 「子供ではあるまいし、自分のことは自分で決めなさい」 (you're not a child, decide your own affairs yourself) — 「〜ではあるまいし」 = it's not as if ～ (so…), used to “first deny some status or situation as a premise, then bring out criticism, reproach, or advice.” It carries an impatient, reasoning tone. This guide covers its feel, the literary roots of 「あるまい,」 and separating it from 「わけではない.」

Core: first say ‘it's not as if ～,' then reason or reproach

「noun ＋ ではあるまいし」 means “it's not as if ～ (so…)” — first denying a premise, then bringing out criticism, advice, or a reason that follows:

• 子供ではあるまいし、そんなことで泣くな (it's not as if you're a child — don't cry over that).
• 新人ではあるまいし、そんな初歩的なミスをするな (it's not as if you're a newbie — don't make such a basic mistake).
• 神様ではあるまいし、未来のことなど分かるはずがない (it's not as if I'm a god — there's no way to know the future).

Feel: 「あるまい」 is the literary negative conjecture of 「ないだろう (surely not ～),」 so 「ではあるまいし」 = “it's not as if ～ (surely you're not ～, are you).” It first denies some status／situation as a premise, then leads into the criticism, reproach, advice of “(since you're not ～, then) you should…／why still…” It carries an impatient, reasoning, mildly reproachful tone. It corresponds to “it's not as if ～, you're not ～ after all (so why still…／so you should…).”

How it attaches

Examples in use

• 一度や二度の失敗ではあるまいし、いちいち落ち込むな。(It's not as if it's your first or second failure — don't get down over each one.)
• プロではあるまいし、そこまで完璧を求めなくてもいい。(It's not as if you're a pro — you needn't demand such perfection.)
• 世界の終わりではあるまいし、そんなに悲観するな。(It's not the end of the world — don't be so pessimistic.)
• 独身ではあるまいし、自分一人で決めるわけにはいかない。(It's not as if I'm single — I can't decide all on my own.)
• 初めて会うわけではあるまいし、そんなに緊張しなくても。(It's not as if we're meeting for the first time — no need to be so nervous.)

⚠️ Easy traps to avoid

① The core is ‘it's not as if ～, so…,' with a critical／reasoning tone. 「〜ではあるまいし」 isn't a neutral negation; it has a very distinct tone — first denying a premise “it's not as if ～,” then leading into criticism, reproach, advice: “(you) it's not as if you're ～, (so why still this／so you should that).” It carries an impatient, reasoning, mildly reproachful or disapproving flavor: 子供ではあるまいし (it's not as if you're a child — implied “you're grown, why still…”), 新人ではあるまいし (it's not as if you're a newbie — “you've done this long, why still make this mistake”). So it's almost always followed by reproach (〜な), advice (〜なさい・〜たら), or a stated reason (〜んだから・〜はずだ). It corresponds to “it's not as if ～, (why still…／you should…).” Test: to say with a touch of reproach “(you) it's not as if you're ～, (so…)” → ではあるまいし.

② Attach noun ＋ ではあるまいし, colloquially 「じゃあるまいし.」 Get the attachment right. It mostly precedes a noun (子供・新人・神様・プロ), and can take a plain form (〜わけではあるまいし). Colloquially it contracts to 「じゃあるまいし」 (では→じゃ): 子供じゃあるまいし (colloquial). It's a set paired expression — a “so…” follow-up (criticism／advice／reason) must come after; you don't stop at 「子供ではあるまいし」 alone. Mnemonic: noun ＋ ではあるまいし (colloquial じゃあるまいし) ＋ (criticism／advice).

③ 「あるまい」 is a literary negative conjecture (= ないだろう) — don't misread it. The 「あるまい」 in 「ではあるまいし」 is the literary auxiliary 「まい」 on 「ある,」 meaning “ないだろう (surely won't／surely isn't),” a negative conjecture. So 「〜ではあるまい」 literally is “surely it's not ～,” and with the cause／adversative 「し,」 「〜ではあるまいし」 = “it's not as if ～ (since surely you're not ～, then…).” Note 「あるまい」 is negative (not affirmative) — don't mistake it for the affirmative “有” just because 「ある」 is there. Likewise, 「まい」 can also express negative volition (never ～) as in 「二度と行くまい (never going again),」 but in 「ではあるまいし」 it's a negative conjecture (surely not). Test: seeing 「ではあるまいし,」 just read it as “it's not as if ～ (so…),” with 「あるまい」 = 「ではない（だろう）.」

🔄 Compare: ではあるまいし／わけではない／じゃあるまいし／まい

💡 The one thing to remember

「〜ではあるまいし」 = it's not as if ～ (so…) — three points: ① the core is “first deny a premise, then bring criticism／reasoning” — an impatient, mildly reproachful tone, followed by reproach (〜な)／advice (〜なさい)／a reason (〜んだから); ② attaches to a noun (colloquial じゃあるまいし), and always has a follow-up; ③ 「あるまい」 is a literary negative conjecture (= ないだろう). This pattern has a real “an elder／been-there person reasoning with you” flavor — 「子供ではあるまいし,」 「新人ではあるまいし」 carry that “you're past this, why still…” exasperation and reproach. To urge someone with a bit of feeling “you're not ～, grow up already,” 「〜ではあるまいし」 is most vivid; but since the tone is reproachful, use it cautiously with superiors or in formal settings.

❓ FAQ

Q: Why does 「ではあるまいし」 carry a reproachful tone? Can I use it in formal settings?

It carries reproach because the structure itself is “first deny the other's excuse／premise, then reason.” 「〜ではあるまいし」 first says “it's not as if ～” (denying a status／situation that could serve as an excuse), implying “since you're not ～ (that forgivable situation), you have no reason to act this way,” then leads into reproach or advice: 子供ではあるまいし、泣くな (you're not a child — don't cry — “a child crying is understandable, but you're grown and still cry, you shouldn't”), 新人ではあるまいし、ミスするな (you're not a newbie — don't slip up — “a newbie's mistake is forgivable, but you're a veteran and shouldn't err”). Its logic is “first remove an exonerating premise, highlighting ‘you have no reason to act this way,'” so it inherently carries impatience, reproach, a reasoning flavor. Therefore, use it very cautiously in formal settings or with superiors／elders — saying 「〜ではあるまいし」 to an elder would seem very rude (like lecturing them). It fits better among peers, juniors, close acquaintances, as an exasperated admonition, or for self-mockery (自分は天才ではあるまいし = it's not as if I'm a genius). Test: to admonish a peer／junior with a bit of feeling “you're not ～, you should…” → usable; with a boss, an elder, in formal settings → avoid, switch to a neutral phrasing (e.g. 「〜ですから、〜」).

Q: Do 「子供ではあるまいし」 and 「子供ではないのだから」 mean the same?

Close in meaning (both “you're not a child, so…”), but different in tone and register. 「子供ではあるまいし」 = you're not a child (impatient, reproachful, reasoning, heavier tone): 「ではあるまいし」 uses the literary 「あるまい (surely not),」 with a stronger, feeling-laden tone, clearly carrying an “exasperated, somewhat impatient” reproach: 子供ではあるまいし、いい加減にしなさい (you're not a child — cut it out — heavy tone, reproachful). It's an emotionally-charged reasoning. 「子供ではないのだから」 = since you're not a child (a more neutral, calm statement of reason): this is a very plain “since it's not ～, then…,” calmly explaining the reason with 「のだから (ので ＋ emphasis),」 not specially reproachful, far more neutral in tone: 子供ではないのだから、自分で判断できるはずだ (since you're not a child, you should be able to judge for yourself — neutrally stating the reason). Difference: 「ではあるまいし」 carries impatience, reproach, feeling (literary, heavy tone); 「ではないのだから」 neutrally, calmly states a reason (colloquial, light tone). Test: to say with feeling, reproachfully “(you) it's not as if you're ～, and still…” → ではあるまいし; to just say calmly, neutrally “since it's not ～, so…” → ではないのだから. Note the direction: 「ではあるまいし」 precedes “the denied status used as an excuse,” so it's 「子供ではあるまいし (not as if you're a child)」 to reproach an adult for being childish. In short, for emotional reproach use 「ではあるまいし,」 for a calm reason use 「ではないのだから」 — different tonal weight.

🖊️ Practice Questions (5)

Q1. 「赤ん坊___、泣けば済むと思うな。」(it's not as if you're a baby)

(A) ではあるまいし　(B) であれば　(C) どころか　(D) ばかりに

Q2. 「ではあるまいし」の後件に来やすいのは?

(A) Rebuke/advice/commentary

(B) Gratitude

(C) Pure time

(D) Objective data

Q3. 「子供ではあるまいし」の意味は?

(A) It's not as if you're a child (so you should...)

(B) Is a child

(C) Wants to be a child

(D) Likes children

Q4. 「ではあるまいし」の語感は?

(A) Using “it's not as if ~” as grounds to lead into a rebuke/advice

(B) Expresses gratitude

(C) Indicates a condition

(D) Indicates purpose

Q5. 接法が正しいのは?

(A) 学生ではあるまいし、責任を持て。　(B) 学生をではあるまいし。

(C) 学生だではあるまいし。　(D) 学生ではあるまいしを。

Answer Explanations

1. (A) ではあるまいし ── It's not as if you're a baby.

2. (A) ── The following clause is usually a rebuke/advice.

3. (A) ── It's not as if you're a child (so you should...).

4. (A) ── Uses “it's not as if ~” to lead into a rebuke.

5. (A) ── 「学生ではあるまいし」 is correct.