The theoretical basis to the notion of immortality lies in the absurdity of death as final. If death is final, then the whole of human life could be regarded as meaningless, since we cannot complete all our aims and aspirations during one brief human lifespan. The only way of fulfilling human potential is by prolonging our lives well beyond the limits of merely physical existence. Sometimes this demand is given a moral twist, so that in the book of Daniel it is said that the need for retribution implies a doctrine of resurrection.