I am not formally trained in Biblical languages (i.e. Hebrew and Koine Greek) nor in Biblical exegesis/exposition. My training is in philosophy so I'll approach the subject from philosophical theology. I agree Biblical exegesis/exposition, and not merely proof texts, should be the basis of any given doctrine affirmed. But it is possible for Biblical evidence to be undetermined in support of a particular doctrine (e.g. Divine Atemporality or Divine Temporality). In such cases, perfect being theology is a minister in our formulation of any given doctrine.
I will assume, for the sake of argument, the Biblical evidence, for the final divine punishment against the wicked, is underdetermined. Thus the Biblical data can equally support eternal conscious torment (ECT) or conditional immortality (CI). I'll summarize each position as I understand it then provide a conceptual analysis of each view. Finally I'll provide an argument in favor of ECT.
Conditional Immortality View
The conditionalist believes life and death are physical. But have a symmetrical spiritual reality. At physical death, people are disembodied yet their souls remain in a temporary state of unconscious sleep until the final judgment. On judgment day God unites souls to resurrected bodies then grants eternal life to believers (conserves their souls/bodies in the New Heavens and New earth) but for unbelievers they are annihilated (God ceases to conserve their souls/bodies in existence). Judgment is a one time temporary event with eternal results.
There seems to be a performative inconsistency in CI
Let's use a transcendental argument and apply it to the doctrine of Hell
(1) If the wicked receive eternal punishment then they exist.
(2) The wicked receive eternal punishment.
(3) Therefore, they exist.
This argument is analogous to Descartes's famous transcendental argument "cogito ergo sum" (i.e. I think therefore I am). Thinking presupposes existence. Likewise, punishment presupposes conscious existence. A counterexample may be provided as capital punishment. A person that dies via capital punishment demonstrates punishment can simply be conscious torment that ends with extinction without any enduring consciousness.
Two problems with the possible counterexample. First, it begs the question on the nature of the soul. It seems to assume death is merely extinction. Second, the possible counterexample, in fact, does not show punishment can exist without conscious existence. It proves quite the opposite. A person cannot receive punishment for a crime without conscious existence. The disagreement is not merely on conscious punishment, it is on the duration of conscious punishment. The duration of conscious punishment is either temporary or eternal. If the former then punishment is temporary but the results are eternal. If the latter then punishment is eternal and the results are eternal. If annihilation is granted then it is not itself punishment but a result of punishment (e.g. pain, mental anguish etc.) since a necessary condition of punishment is conscious existence.
There is a presumption of hell (as eternal conscious torment) in virtue of God's holiness and the severity of sin. This belief can be deduced from perfect being theology. Soul sleep is denied in favor of some form of substance interaction dualism. Humans are understood as holistic composite beings with physical bodies that are animated by incorporeal souls. At physical death our disembodied souls go to the intermediate state of either paradise with God or conscious torment until the day of judgment. On judgment day God unites all souls to resurrected bodies. God judges all people. Believers are transformed to possess glorified bodies and granted crowns based on merits. They are to be an eternal witness/exhibition of God's Grace to the glory of God. God forever conserves their souls/bodies in the New Heavens and Earth.
Unbelievers remain as objects of God's wrath. God concurs with unbelievers insistence to exist divorced from God. God gives unbelievers over to their self-destructive desires. God places unbelievers in Hell. They are to be an eternal witness/exhibition of God's justice to the glory of God. God forever conserves their souls/bodies in existence. The eternal conscious torment experienced by unbelievers are self-inflicted. It is perpetually sustained by their fixed unbelief. Hell is absence of joy, fulfillment, pleasure, delight or a personal relationship with God. In fact, unbelievers in Hell have lost their personal identities. They point to their fixated collection of sins as their identities.
1. The Old Testament should be interpreted in light of the New Testament. Types/shadows in Old Tokens/Substance in the New Testament. Progressive Revelation is predicate on God's revelation gradually disclosed more information with greater clarity.
2. The intuitive nature of Justice. Any given punishment must be proportionate to the crime. If we offend or dishonor an infinite God we deserve an infinite punishment.
(1) If hell is not eternal conscious torment then sin is not an infinite offense against God.
(2) Sin is an infinite offense against God.
(3) Therefore, hell is eternal conscious torment
3. Annihilation is a minimal punishment. Eternal conscious torment is a maximal punishment.
(1) If God is a maximally great being then His attributes are maximally great.
(2) God is a maximally great being
(3) Therefore, His attributes are maximally great.
(4) If God expresses the attribute of Justice then Justice is expressed in a maximally great way.
(5) God will express Justice in the final punishment of the wicked
(6) Justice will be expressed in a maximally great way.
It is granted premise (4) can be disputed on the grounds God is not obligated to express any given attribute nor must it be expressed in a maximally great way. In fact, if God so chooses He can express any of His attributes in a minimally great way. Thus it is dependent upon God's choice. Premise (4) can be reformulated to be immune to such an objection. Let (4*) replace (4):
(4*) If God chooses to expresses the attribute of Justice then Justice is expressed in either a minimally great way or a maximally great way.
(7) Either annihilation is a maximally great punishment or eternal conscious torment is a maximally great punishment.
(8) Annihilation is not a maximally great punishment.
(9) Therefore, Eternal conscious torment is a maximally great punishment.
Assuming (3), (6) and (9) we deduce:
(10) If Justice is expressed in a maximally great way then eternal conscious torment is the final punishment of the wicked.
(11) Justice is expressed in a maximally great way
(12) Eternal conscious torment is the final punishment of the wicked.
(1) There is a possible world in which God, in all possible worlds, expresses his attribute of Justice in final punishment of the wicked with eternal conscious torment.
(2) The actual world is a possible world.
(3) Therefore, God expresses his attribute of Justice in final punishment of the wicked with eternal conscious torment in the actual world.
What if the traditionalist denies the immortality of the body?
Or what about eternal unconscious existence? Eternal unconsciousness
Dead spiritually in what sense? Is the reprobate in the same condition pre after life as after life?
What is death?
There is a pragmatic argument to be made too:
(1) If hell is annihilation then the punishment for sin is not the most severe.
(2) Hell is annihilation
(3) Hence, the punishment for sin is not the most severe.
If premise (1) is granted the punishment provides little incentive to deter/restrain sin. It further removes motivation from the unbelieving.