Man dies of cold, not of darkness.

The aphorism contrasts two kinds of deprivation: “darkness” as ignorance, uncertainty, or lack of intellectual clarity, and “cold” as the absence of human warmth—love, compassion, solidarity, or spiritual consolation. Unamuno’s thought often insists that people can endure not-knowing (even profound metaphysical doubt) better than they can endure emotional abandonment or a world stripped of fellow-feeling. The line suggests that what truly destroys a person is not the mind’s obscurity but the heart’s chill: a life without warmth, hope, or communion. It also implies a critique of purely rational “light” as insufficient; survival depends less on certainty than on sustaining warmth in relationships and meaning.