No one really knows why they are alive until they know what they'd die for.

The line frames purpose as inseparable from moral commitment: a life’s meaning becomes clear only when a person identifies a cause or principle worth ultimate sacrifice. It echoes themes common in King’s rhetoric—courage, disciplined nonviolence, and the demand that conscience override comfort—by suggesting that authentic living requires more than self-preservation. The quote also functions as a critique of complacency: without a “why” strong enough to risk loss, one drifts through life without a settled identity or vocation. In this sense, “die for” need not be literal; it can signify steadfastness under pressure, willingness to suffer consequences, and prioritizing justice over personal security.