oh hey, a fellow annihilationist! out of curiosity what's your rationale behind that belief?
Hi! Please forgive the long reply, but I've been wanting to discuss this for some time, so do bear with me.
I found my way to annihilationism after being dissatisfied with the doctrine of eternal conscious torment, which was the standard belief in the environment I grew up in. I just couldn't reconcile the idea of a God Who is Love with the notion that He would condemn any person to an eternity of suffering for a finite amount of rebellion; the punishment seems comically disproportionate to the crime. When I started doing some research into the fate of the unsaved, I learned that eternal torment was merely an interpretation of scripture, not a fact directly stated by it, and so I explored other interpretations. Universalism certainly has its appeal, and I personally think purgatorial universalism is very in-line with the character of God, but I can't reconcile universalism with scripture. To me, annihilationism seems to be the school of thought that best aligns with the known character of God while still having scriptural support.
I find scripture (mostly NT of course) to be fairly clear that not all will be saved, but that at least some will be condemned at the final judgement. And when discussing the fate of the wicked, Jesus says multiple times in Matthew 13 that they will be thrown into a furnace and burned like weeds (13:30, 40-42) and bad fish (13:47-50). The analogy here implies that the wicked will be utterly burned up and consumed.
Similarly, Revelation (mostly chs. 20 and 21) discusses the lake of fire, which is also called "the second death." The text says that six distinct things will be thrown into the lake of fire: the beast and the false prophet (19:20), the devil (20:10), Death and Hades (20:14), and "anyone whose name was not found written in the book of life" (20:15) (this last group can be conflated with the people mentioned in 21:8). Notably, the text only specifies that the first three—the beast, the false prophet, and the devil—"will be tormented day and night forever and ever" (20:10). In the very same paragraph, the (presumably human) armies of Gog and Magog are utterly consumed by fire from heaven, not explicitly cast into the lake of fire; therefore, even if the lake of fire is always supposed to be an eternal torment, we are also given a potential example of wicked humans who are not sent there but are instead completely destroyed.
Also of note is that Death and Hades are cast into the lake of fire after giving up their dead (20:14). John of Patmos considers these to be places where the dead reside before the final judgement (20:13), so if the lake of fire is always supposed to be eternal torment, what sense does it make to send empty, impersonal realms there? Rather, this to me indicates that the lake of fire is capable of total destruction. Supporting this idea is the fact that the lake of fire is called "the second death" only when pertaining to Death, Hades, and humans (20:14-15, 21:8, and probably 20:6 and 2:11), i.e. the things not explicitly stated by the text to suffer forever. Therefore, the lake of fire is the second death, i.e. total destruction, for Death, Hades, and humans, but it is eternal torment for the beast, the false prophet, and the devil.
The usual counterargument against annihilationism from scripture is that there are verses which speak of the fate of the wicked/ungodly as "eternal" (e.g. Daniel 12:2, Matthew 18:8 and 25:41, Mark 9:48). In these cases, I believe the phrases like "eternal fire" and "everlasting contempt" are best interpreted as meaning that the punishment is eternal in the sense that it is imposed forever and there is no coming back from it. If the unsaved are completely annihilated and cease to exist, then there's certainly no coming back from that. Likewise, "eternal fire" means that the fire into which the unsaved are cast can never be put out, so if one is sent into the fire, there is nothing that can be done to stop them from being wholly burned up by it.
This also gets into the question of the immortality of the human soul. Personally, I think God is more than capable of both granting and taking away immortality to souls. As Jesus says in Matthew 10:28, "Do not fear those who kill the body but cannot kill the soul; rather, fear the one who can destroy both soul and body in hell [or Gehenna]."
Finally, many Christians today like to describe hell as 'total separation from God.' I don't necessarily disagree, but think about it. God not only created, but sustains all things (see Hebrews 1:3). Things only continue to exist because God sustains their existence. If one were wholly separated from God, then one would be cut off from God's sustaining presence, which would probably cause one to cease to exist.
Do I claim absolute certainty in my belief in annihilationism? No. At the end of the day, it's just my best guess based on my understanding of the evidence. Like the good little Anglican that I am, I don't think the specific fate of the unsaved should be required dogma, especially because it really shouldn't impact our daily living out of the faith very much. If you actually read all this, thank you for bearing with me!