“〜wake ga nai・〜wake ni wa ikanai”: Impossibility vs (Moral) Obligation [JLPT N3-N2]
Content by NTJ Kuma · Nihongo to Japan editorial team · Updated July 27, 2026
「受かるわけがない」vs「休むわけにはいかない」 — logically impossible vs can't (out of duty).
「そんな話、本当なわけがない！」 — there's no way it's true
「宝くじが当たった？そんな話、本当なわけがないでしょ」 (won the lottery? there's no way that's true) — 「〜わけがない」 is strong negation: “there's no way ～, couldn't possibly ～,” flatly asserting something has no grounds to hold. This guide covers 「わけがない」's use and attachment, separating it from the ‘partial negation' 「わけではない」 and the inferential 「はずがない」.
Core: couldn't possibly ～ (a strong, assertive negation)
「(plain form) ＋ わけがない」 = “there's no way ～, couldn't possibly ～” — asserting “(by reason) it's simply impossible,” in a strong, positive tone:
- こんな難しい問題、子供に解けるわけがない (there's no way a child can solve such a hard problem).
- 彼がそんな嘘をつくわけがない (there's no way he'd tell such a lie).
Feel: “how could …／there's no way …” — the core is “by common sense, asserting something has no possibility,” with strong subjective conviction. Colloquially also 「わけない」 (dropping が). It's the strongest negation in the 「わけ」 family.
Attachment
| Word class | Form | Example |
|---|---|---|
| verb | plain form ＋ わけがない | 勝てるわけがない （there's no way we can win） |
| i-adjective | plain form ＋ わけがない | 安いわけがない （there's no way it's cheap） |
| na-adjective | 〜な ＋ わけがない | 簡単なわけがない （there's no way it's easy） |
| noun | 〜な ＋ わけがない | 本当なわけがない （there's no way it's true） |
See it in context
- 練習もしないで、上手になるわけがない。(Without even practicing, there's no way you'll get good.)
- あの真面目な人が、遅刻するわけがない。(Such a serious person couldn't possibly be late.)
- 一日で治るわけがないでしょう。(There's no way it heals in a day.)
- こんな高い時計、私に買えるわけがない。(There's no way I could afford such an expensive watch.)
- 彼女が君のことを忘れるわけがないよ。(There's no way she'd forget you.)
⚠️ Common mistakes to avoid
① 「わけがない」 (impossibility) ≠ 「わけではない」 (it's not that). The most-mixed pair in the 「わけ」 family, worlds apart in strength. わけがない = couldn't possibly ～ (total, strong negation, assertion) (できるわけがない = there's no way I can); わけではない = it's not that ～ (partial negation, mild, leaving room) (できないわけではない = it's not that I can't [just …]). For an assertive “couldn't possibly” use わけがない, for an indirect “it's not that” use わけではない. One 「が／では」 apart — one total, one partial. (わけではない: see 〈わけではない〉.)
② 「わけがない」 (asserted impossibility) vs 「はずがない」 (inferred impossibility) differ in tone. Both render as “impossible,” but わけがない is more subjective, stronger, more colloquial (asserting “how could it” by common sense/emotion); はずがない is more rational, grounded (inferring “by reason it shouldn't/wouldn't” from a premise). 彼が犯人なわけがない (there's no way he's the culprit — strong emotional assertion) vs 彼が犯人なはずがない (he shouldn't be the culprit by reason — a grounded inference). For a strong assertion use わけがない, for “by reason it wouldn't” use はずがない.
③ Attachment: na-adjectives・nouns add 「な」. Na-adjectives・nouns don't attach directly. na-adjective ＋ な (無理なわけがない), noun ＋ な (本物なわけがない). Only verbs・i-adjectives attach the plain form directly (勝てるわけがない, 安いわけがない).
🔄 Nuance & comparison: わけがない／わけではない／はずがない／っこない
| Form | Feel | Example |
|---|---|---|
| 〜わけがない | couldn't possibly ～ (strong assertion, subjective) | できるわけがない （there's no way I can do it） |
| 〜わけではない | it's not that ～ (partial negation, leaving room) | できないわけではない （it's not that I can't do it） |
| 〜はずがない | shouldn't ～ by reason (inferential negation, more rational) | 来るはずがない （there's no way they'd come） |
| 〜っこない | no way ～ (colloquial, very casual) | できっこない （no way that's happening） |
💡 The key point in use
「〜わけがない」 = there's no way ～, how could ～, the strongest negation in the 「わけ」 family: by common sense or emotion, flatly asserting “something has simply no grounds to hold” (練習しないで上手になるわけがない = no way you'll improve without practicing; 彼が嘘をつくわけがない = there's no way he'd lie). Three points: ① most needs separating from 「わけではない」 — わけがない = couldn't possibly (total negation, assertion), わけではない = it's not that (partial negation, leaving room), one total, one partial; ② tone difference from 「はずがない」 — わけがない is more subjective, strong, colloquial (how could it), はずがない more rational and grounded (by reason it wouldn't); ③ attachment — na-adjective・noun ＋ な, colloquially dropping が → 「わけない」. For a strong “couldn't possibly,” わけがない has the most force. (It's not that: 〈わけではない〉; can't: 〈わけにはいかない〉; family: 〈わけだ〉.)
❓ Quick FAQ
Q: 「わけがない」 and 「はずがない」 both mean ‘impossible' — how do I tell them apart?
Both mean “impossible, wouldn't,” differing in subjective strength vs rational inference. 「〜わけがない」 = couldn't possibly ～ (more subjective, stronger, more colloquial, often an emotional assertion “how could it!”): あの人が犯人なわけがない！ (there's no way that person's the culprit! — strong emotional conviction, almost blurted out); こんな簡単なミス、彼がするわけがない (there's no way he'd make such a simple mistake — a strong assertion). Its negation is flat, with subjective emotion. 「〜はずがない」 = shouldn't ～ by reason, wouldn't by logic (a more rational, grounded inference from a premise/common sense): 彼は今日休みだから、会社にいるはずがない (he's off today, so by reason he wouldn't be at the office — inferring from the “off” premise); あんなに勉強したのだから、落ちるはずがない (having studied so hard, by reason he wouldn't fail). Its negation is based on some reason or premise, cooler. Test: for a strong, subjective “how could it, no way” → わけがない; for a rational “by reason it wouldn't” → はずがない. Often swappable (彼が来るわけがない／はずがない), but わけがない is more emotional and flat, はずがない more like a grounded inference.
Q: 「わけがない」 vs 「わけではない」 — which is ‘impossible' and which is ‘it's not that'? I keep reversing them.
Remember 「が」 maps to strong negation, 「では」 to weak (partial) negation: 「わけ『が』ない」 = impossible (strong, total negation) — 「が」 makes it “there's ‘no' (grounds) to hold” = “couldn't possibly”: そんなこと、あるわけがない (there's no way that exists — total negation). 「わけ『では』ない」 = it's not that (indirect, partial negation) — 「では」 makes it “(it's not) ‘that way'” = “not entirely, it's not that”: 嫌いなわけではない (it's not that I dislike it — partial negation, leaving room). Memory aid: 「が」 → “how could it” (strong); 「では」 → “it's not (that way)” (weak, leaving room). Or lock it with a contrast pair: 「嫌いなわけがない」 = there's no way I dislike it (asserting I like it); 「嫌いなわけではない」 = it's not that I dislike it (maybe just not especially fond). One is “no such possibility” (total negation), one “not entirely so” (partial negation) — see 「が」 think strong, see 「では」 think weak, and you won't reverse them. (Partial negation: see 〈わけではない〉.)
🖊️ Practice Questions (5)
Q1. 「彼はずっと働いている。疲れていない___。」 (no way he isn't tired — a logical judgment)
(A) わけがない (B) わけにはいかない (C) はずがない (D) べきではない
Q2. 「チームメンバーを裏切る___。」 (morally can't betray teammates)
(A) わけがない (B) わけにはいかない (C) はずがない (D) べきではない
Q3. 「勉強もしないで、試験に受かる___。」 (no way you pass without studying)
(A) わけがない (B) わけにはいかない (C) ようがない (D) しかない
Q4. 「病気だけど、今日は会議があるから、休む___。」 (even if sick, can't take the day off)
(A) わけがない (B) わけにはいかない (C) はずがない (D) 必要がない
Q5. 「行か___わけにはいかない。」 (not going is not an option = I must go)
(A) ない (B) なく (C) ず (D) ないで
Answer Explanations
1. (A) わけがない ── 「ずっと働いている (has been working the whole time)」 → logically certain that "there's no way he isn't tired" → わけがない (logical certainty).
2. (B) わけにはいかない ── 「チームメンバーを裏切る (betray teammates)」 = something you morally can't do → わけにはいかない (a moral/situational barrier).
3. (A) わけがない ── 「勉強もしないで合格 (passing without even studying)」 = a commonsense logical impossibility → わけがない.
4. (B) わけにはいかない ── 「病気だけど会議がある (there's a meeting, so can't take off)」 = a situational barrier, unavoidable → わけにはいかない.
5. (A) ない ── 「行かないわけにはいかない」 = not going is not an option (a double negative = obligation). Attachment: verb ない-form + わけにはいかない.