Used to show a strong assertion or emphasis on one's opinion; 'isn't it', 'aren't you', 'right'.
Long explanation:
The ~ではないか grammar point is used to indicate a strong assertion or emphasize one's opinion. It can be translated as 'isn't it', 'aren't you', or 'right' in English. It is formed by adding ではないか to the end of a sentence to turn it into a rhetorical question.