Every one of us is, in the cosmic perspective, precious. If a human disagrees with you, let him live. In a hundred billion galaxies, you will not find another.

Carl Sagan’s line is associated with his late–Cold War/early post–Cold War humanist appeals for humility and tolerance grounded in astronomy—his recurring argument that seeing Earth in its true cosmic setting should soften dogmatism and tribal hostility. The wording is widely circulated as a Sagan quotation and is often linked by readers to the themes he developed in the “Pale Blue Dot” era: the rarity of individual human lives against an immense universe, and the ethical implication that disagreement is not a justification for dehumanization. However, I cannot confidently identify the exact occasion (speech, interview, or chapter) in which Sagan delivered this precise phrasing.

The quote fuses two ideas Sagan repeatedly paired: cosmic insignificance in scale and personal significance in uniqueness. “Cosmic perspective” reframes everyday conflicts—political, religious, interpersonal—as small against the backdrop of billions of galaxies. Yet the conclusion is not nihilism; it is moral restraint. Because each person is a singular, unrepeatable configuration of consciousness and experience, the proper response to disagreement is tolerance (“let him live”), not coercion or violence. The rhetorical pivot from vastness (“hundred billion galaxies”) to the irreplaceability of one human being turns astronomy into an ethical argument for pluralism and compassion.