modality N2 common politewritten
〜のではないだろうか — isn't it (perhaps) that ~?
〜のではないだろうか ・ のではないだろうか
Builds on だろう
Meaning
- isn't it perhaps that ~? / I rather think ~ — a softened assertion phrased as a tentative question to the reader or listener
Key sentence
この案には問題があるのではないだろうか。
Isn't there perhaps a problem with this proposal?
Formation
| Attaches to | Form | Example |
|---|---|---|
| Clause (plain) + のではないだろうか | [plain clause] + のではないだろうか / のではないでしょうか (polite) | 無理なのではないだろうか |
When: Formal-leaning; a hedging device that floats the speaker's own view as a question — softer and more persuasive than a flat assertion. Polite form: のではないでしょうか.
Examples
もっと別のやり方があるのではないだろうか。
Mightn't there be some other way to do this?
彼は本当は知っていたのではないだろうか。
I rather suspect he actually knew.
When you can't use it
- Despite the question shape, it conveys the speaker's tentative opinion ('I think ~, don't you?'), not a genuine request for information.
Easily confused with
〜のだろうか のだろうか is genuine introspective wondering ('I wonder if ~'); のではないだろうか leans toward an affirmative hunch the speaker half-believes ('isn't it actually the case that ~?'). 〜じゃないか じゃないか is the blunt spoken 'isn't it ~?'; のではないだろうか is its formal, more tentative and polite cousin used in writing and careful speech.
See 〜のではないだろうか in real sentences
Jengo shows 〜のではないだろうか the way you actually meet it: inside real Japanese sentences, so it sticks instead of staying an abstract rule.
Study it in JengoSources Compiled from published Japanese grammar references.