The Tragic Sense of Life is Unamuno's masterpiece of existential philosophy, a passionate argument that the desire to live forever — not to know truth, but to go on living — is the bedrock of all genuine philosophy and religion. Written against the cold rationalism of positivist Europe, Unamuno insists that the conflict between reason, which destroys immortality, and the heart, which hungers for it, cannot be resolved but must be lived. This irresolvable contradiction — the tragic sense — is not a problem to be overcome but the very substance of the fully human life. Published in Spanish in 1912, it influenced Sartre, Camus, and the whole tradition of European existentialism.