As the separation of the soul from the body is the death of the body, so the separation of God from the soul is the death of the soul. And this death of the soul is the true death. This is made clear by the commandment given in paradise, when God said to Adam, ‘On whatever day you eat from the forbidden tree you will certainly die’ (cf. Gen. 2:17). And it was indeed Adam’s soul that died by becoming through his transgression separated from God; for bodily he continued to live after that time, even for nine hundred and thirty years (cf. Gen. 5:5).
The death, however, that befell the soul because of the transgression not only crippled the soul and made man accursed; it also rendered the body itself subject to fatigue, suffering and corruptibility, and finally handed it over to death. For it was after the dying of his inner self brought about by the transgression that the earthly Adam heard the words, ‘Earth will be cursed because of what you do, it will produce thorns and thistles for you; through the sweat of your brow you will eat your bread until you return to the earth from which you were taken: for you are earth, and to earth you will return’ (Gen. 3:17-19).
Even though at the regeneration to come, in the resurrection of the righteous, the bodies of the godless and sinners will also be raised up, yet they will be given over to the second death, age-long chastisement, the unsleeping worm (cf. Mark 9:44), the gnashing of teeth, the outer, tangible darkness (cf. Matt. 8:12), the murky and unquenchable fire of Gehenna (cf. Matt. 5:22), in which, as the prophet says, the godless and sinners ‘will be burned up together and there will be none to quench the flame’ (Isa. 1:31). For this is the second death, as St. John has taught us in the Revelation (cf. Rev. 20:14). Hark, too, to the words of St. Paul, ‘If you live in accordance with your fallen self, you will die, but if through the Spirit you extirpate the evil actions of your fallen self, you will live’ (Rom. 8:13). Here he speaks of life and death in the age to be: life is the enjoyment of the everlasting kingdom, death agelong chastisement.
Thus the violation of God’s commandment is the cause of all types of death, both of soul and body, whether in the present life or in that endless chastisement. And death, properly speaking, is this: for the soul to be unharnessed from divine grace and to be yoked to sin. This death, for those who have their wits, is truly dreadful and something to be avoided. This, for those who think aright, is more terrible than the chastisement of Gehenna. From this let us also flee with all our might. Let us cast away, let us reject all things, bid farewell to all things: to all relationships, actions and intentions that drag us downward, separate us from God and produce such a death. He who is frightened of this death and has preserved himself from it will not be alarmed by the oncoming death of the body, for in him the true life dwells, and bodily death, so far from taking true life away, renders it inalienable. (To the Most Reverend Nun Xenia 9-12)
Death is thus a kind of protracted process or, rather, there are myriads of deaths, one death succeeding the next until we reach the one final and long-enduring death. For we are born into corruption, and having once come into existence we are in a state of transiency until we cease from this constant passing away and coming to be. (Topics of Natural and Theological Science and on the Moral and Ascetic Life: One Hundred and Fifty Texts, 52)