JLPT N1
～でなくてなんだろう
must be; is definitely; if it's not [X], what is it?
Structure / Usage
Noun + でなくてなんだろう
Example Sentences
これが愛でなくてなんだろう。
If this isn't love, then what is?
彼の行動が勇気でなくてなんだろう。
His actions are definitely courage—what else could they be?