What is the spiritual concept of death?

But for that which we call death—

We would have no mental air to breathe. The higher strata of existence would be cut off. The supersensuous nature would be starved. We would be stifled and famished in the prisonhouse—the little, feeble spark of life would die out, leaving the body shriven, shrunken and a lifeless automaton. That vital breath, that living condition of being, that sheltering and protecting power, that harmony and splendour of all things—you would not be reading these words—there would be nothing to move you here. The spiritual impulses of the universe would be forgotten—there would be no fountains of inspiration, no thought of religion, no touchstone to immortality.