From Apocalypse Explained ~ Emanuel Swedenborg
[T]he essential life of man is his spiritual life, for it is through this that he is a man and is distinguished from beasts, which have only natural life. In man the natural life without the spiritual life is dead, since it has not in itself heaven, which is called "life" and "eternal life," but has hell, which is spiritually called "death." In the Word, the "dead" mean those who live a natural life only, and not at the same time a spiritual life; also "death," in reference to man, means a lack of the faculty of understanding truth and perceiving good; and this lack exists when the internal spiritual man has not been formed, for this is formed by means of truths from good. In that internal man the ability to understand truth and perceive good has its seat, for that man is in heaven and in its light, and he who is in the light of heaven is a living man. But when the natural man only has been formed, and not at the same time the spiritual, there is no faculty of understanding and perceiving the truths and goods of heaven and the church, because that man has no light from heaven. For this reason such a man is called "dead."
(Apocalypse Explained 694)