〜ようではないか

〜ようではないか is a strong, sometimes slightly masculine exhortation used to propose a course of action. It pairs the volitional form of a verb (or a related suggestion) with ではないか to turn the statement into a friendly challenge or invitation. It carries a sense of “Let’s …” or “Why don’t we …” and is common in group situations, workplaces, or when addressing friends or juniors. It can sound motivational, motivational, or even rhetorical, depending on tone. Typical contexts include proposing a plan, encouraging action, or nudging others to agree on a course of action. The form is most natural with verbs in the volitional (行こう、しよう、やろう), but extended usages with nouns or な-adjectives occasionally appear in more formal or literary speech in the pattern of a proposal or suggestion.