ないわけにはいかないCannot avoid doing; have to
Use this when duty, a promise, a relationship, reputation, or practical circumstances make not doing something feel impossible. It often suggests that the person might prefer not to act but sees no acceptable alternative.
How the two negatives work
The first negative describes the option of not acting. The rest of the construction rejects that option. Thus 行かないわけにはいかない means that not going is not realistically acceptable, so the person has to go. This is more than an abstract double negative: the context should provide a believable source of pressure.
Typical sources of obligation
The reason is often stated directly so that the listener can see why non-action is not a real option.
約束した以上、明日の会議には出ないわけにはいかない。
Since I made a promise, I can't very well skip tomorrow's meeting.
AnalyzeThe promise creates a personal and social obligation.
母が入院しているので、しばらく店を手伝わないわけにはいきません。
Since my mother is in the hospital, I have no choice but to help at the shop for a while.
AnalyzeThe family situation makes refusing to help feel untenable.
主将である以上、彼も責任を取らないわけにはいかない。
As team captain, he cannot avoid taking responsibility.
AnalyzeThis third-person example presents responsibility as arising from the person's role.
A reluctant decision
今日も残業するの？
Are you working late again today?
Analyze明日が締め切りだから、今夜中に終わらせないわけにはいかないんだ。
The deadline is tomorrow, so I have to finish it tonight.
AnalyzeThe speaker is not simply stating a schedule; the deadline removes the option of leaving the work unfinished.
Choosing among similar forms
行くわけにはいかない means that circumstances prevent going, while 行かないわけにはいかない means that circumstances prevent not going. ざるを得ない has a similar “no alternative” meaning but is more compact and generally more written-leaning. Basic forms such as なければならない state necessity directly; the target construction more clearly presents non-action as unacceptable because of the surrounding circumstances.
More examples
引き受けた以上、最後までやり遂げないわけにはいかない。
Now that I've accepted the responsibility, I have to see it through to the end.
Analyze親友にそこまで頼まれたら、力を貸さないわけにはいかない。
If a close friend asks me that earnestly, I can't very well refuse to help.
Analyzeこのまま赤字が続けば、経営計画を見直さないわけにはいかない。
If the losses continue like this, we will have to review the business plan.
Analyze昨日は担当者が休んだため、私が対応しないわけにはいかなかった。
The person in charge was absent yesterday, so I had to step in.
Analyze事実を知っている以上、彼女も証言しないわけにはいかないだろう。
Since she knows the facts, she probably cannot avoid testifying.
Analyze皆が準備を進めてくれたので、今さら計画を中止しないわけにはいかない。
Everyone has worked on the preparations, so at this point we cannot avoid canceling the plan.
AnalyzeHere practical circumstances make cancellation unavoidable despite the effort already invested.