We are all subject to the fates. But we must act as if we are not, or die of despair.

The line sets up a tension between determinism (“subject to the fates”) and the psychological necessity of agency. Even if larger forces—chance, history, biology, power—shape outcomes, a human life becomes unlivable if one treats those forces as absolute. Pullman’s phrasing suggests that hope and moral responsibility depend on behaving as though choices matter: acting, resisting, and committing oneself to purposes despite uncertainty. The alternative is paralysis and nihilism (“die of despair”). The quote thus frames agency less as a metaphysical claim to total freedom than as an existential practice required for courage, ethics, and endurance.