No religion here, but Christ likens death to a sleep.
Upon death (unless one is in Christ) a person goes down to the world of the dead (Sheol/Hades). Here, the dead are conscious of nothing. They are sleeping, awaiting the resurrection (the second resurrection, the resurrection of the dead).
At that resurrection (of the dead), Hades (the world of the dead) gives up the dead that are in it.
And the sea gave up the dead who were in it, Death and Hades gave up the dead who were in them, and they were judged, each one of them, according to what they had done. Rev 20:13
If the dead had ceased to exist, if the dead were not in Hades, then Hades would have nothing to give up at this time.
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If one is IN Christ, one still sleeps until the first resurrection, but one does so 'under the altar' (in the spiritual realm). Hence, Stephen called out to Christ to receive his spirit (at his execution).
Peace again to you!
your servant and a slave of Christ,
tammy