There are many serious problems to the conditional view. First, in the creation of man, the Hebrew plural is used translated as a signular "life" in Gen. 2:7.
When you claim there are "serious problems" in someone's view, the first thing you list should be an actual problem, not just an observation about an untranslated grammatical detail. A "problem" should involve an actual Biblical teaching, not your personal opinion caused by reading between the lines of a grammatical irregularity!
And this is indeed only your opinion. The experts disagree with you. BDB says chayyim is a "pl. abs. emph.", or a plural of emphasis (abs. means it's absolute, rather than construct). Scanning through the Bible's use of the word, I find many cases where chayyim is used to refer to a single finite lifespan, as for example Ex 6:16 "the length of Levi's life was 137 years." (BDB lists hundreds.) Another is Lev 18:8, forbidding marrying the sister of your wife during her chayyim (life). Note that this is certainly her earthly life -- levirate marriage requires marrying a sibling of your spouse. Then there's Gen 7:15 - "And they came to Noah to the ark, two of each, from every living thing in which was the breath of life." Not only the same word, but the same EXPRESSION, but about animals.
More examples which actually bear on this argument include: "He asked You for life, and You gave it to him-- length of days forever and ever." (Ps. 21:4 CSB) And yes, this is "chayyim" He's asking God for. Notice that the result of Him asking God is "length of days for ever and ever" -- a strong statement, and standalone proof of conditional immortality, since it shows that "length of days forever" is conditional on "asking God", not simply something everyone gets. Much the same is stated in Romans 2:6-7 - "He will repay each one according to his works : 7 eternal life to those who by patiently doing good seek for glory, honor, and immortality..." Again, life and immortality (deathlessness) are both gifts of God, made ultimate to those God rewards in the final judgment but denied to those He punishes.
Prior to the Babylonian captivity the Hebrew plural did not refer to a plural of majesties but to three or more in contrast to the hebrew singular and dual.
You are simply wrong, and there are very many direct counterexamples in the Bible. So why should your non-fact be listed as the first element in a case against conditionalism? It's not even true; but almost worse, it's not an argument against conditionalism even if it were true.
God created man in his own "image" and part of that image as a "spirit" being is a spiritual image as well as a triune image.
There's no Biblical reason to accept that this is what "God created man in His own image" means. The Bible exegetes the image of God in 4 passages: Gen 1:26 (it means we are to rule over all beasts); Gen 9:6 (it means murderers must be executed); Luke 20:24 and parallels (it means we owe ourselves to God); and James 3:9 (it means our treatment of men reflect our true opinion of God). None of this hints at your strange triple-life interpretation, and absolutely none of it reflects badly on my claim, that life is a finite gift of God and not EVER an eternal curse.
Man was created with a plurality of lives (1) biological life; (2) spiritual life; (3) soul life.
You need to connect the dots between this truth, and your claim that this is a "serious problem" to conditionalism -- even if everything you'd stated were true, it wouldn't follow that conditionalism is false. Suppose that we're actually supposed to have three different lives in our three different parts. Then it follows that each life belongs to its own specific part, and when the life of a part ends that part dies. The body's life ends when the body dies. Conditionalism's claim is that in the final judgment, the life of the soul will be taken and the soul itself, along with the body and like the spirit, will finally and utterly die.
This is what it means for a thing to _die_ -- it means its life ends. Every dictionary in the world, in EVERY language, agrees with me.
The Ephesians had both biological and soul life but their spirit was "dead" due to sin. It was their "spirit" that was "dead" due to sin because Jesus denies that what is born of the Spirit is "flesh" but rather what is born of the Spirit is "spirit."
You're making random guesses, not actual statements about the clear teaching of Ephesians. Paul didn't anywhere in the book say that their spirit was dead; he said that "you were dead." In fact, Paul mentions a spirit in a human only once in the entire book, in the phrase "renew the spirit of your mind."
In Ephesians 2:1, 5 what is "quickened" is not biological death (the body) or the soul but the "spirit" of man.
By putting quotes around "spirit" you give the false impression that Paul actually said "spirit" and you're quoting him. But in reality it's all you, making things up that Paul didn't say. That's your problem, not mine.
Hence, "death" does not equal annihilation with regard to the spiritual make up of man but equals separation from God. Their "spirit" was not non-existent ...
Death does not equal annihilation or non-existence. The wicked will be killed by God (Luke 12:5, Isa 66:16) and destroyed by God (Matt 10:28, Mal 4:1-3), not because death and destruction are "equal," but because God will do both things.
as it [their spirit] was very active in the cause of Satan (Eph. 2:2-3; 4:18-19).
This passage does not teach they were both dead and active at the same time and in the same way (specifically in their spirit), which is what you claim. Rather, this passage uses "dead" metaphorically, just as Romans 6:11 does; the unsaved are active toward sin, while at the same time being dead to God; and the saved should be dead to sin and alive (active) to God. Your past attempts to deny this metaphor have never dealt with its opposite in Romans 6:11.
Physical death cannot make spiritual life cease to exist (Mt. 10:28)
Of course death in the body need not affect the spirit. This is the big difference between the punishment God imposes and the punishment man imposes, after all -- God's punishment DOES affect the spirit. The reason He says to fear (obey) God rather than man is that although men CLAIM to be able to preserve your soul by not killing you, they have no power to actually save your life. So whoever saves their own life will lose it, and whoever loses their life for the sake of the gospel will save it. Conditionalism, pure and simple.
At physical death the "spirit" of man does not return to dust but to God. It is only the body and biological life that ceases and returns to dust.
This is only true about *physical death*, and this is WHY it's called physical death; it's because it only affects the body. But this is Jesus' point -- God can kill AND destroy both body and soul! The final judgment will kill all parts of man, and finally, "you will return to dust" will be completely true.
Hence, the spirit of man continues to exist and Jesus claims it continues to exist at least up to the final judgment and only rendered usless in Gehenna rather than being annihilated in Gehenna.
Jesus teaches that the soul of man is DESTROYED in gehenna along with the body. He says nothing about "only rendered useless rather than being annihilated"; on the contrary, of the available Greek words for destruction, He uses one of the strongest; and far from offering the "rather than" qualification you're eisegeting, He's saying it in order to stress God's unique power to do things man CANNOT.
If any translator believed that Jesus really meant "only rendered useless" in this passage, they could easily have translated it that way. They don't, because that's not what it means.
Furthermore, there is no passage in the entire Bible teaching anything like your claim that the wicked will be rendered useless but not destroyed. The Bible teaches from front to back that the wicked will be killed, destroyed, turned to ash, will not attain to the age to come, will not have a part in the New Creation, will cease to be, will "be as though you had not been"... It says that the fires of judgment will do to them what unquenchable fire does to chaff, tares, thorns, dead trees, cut-off vines... when the Bible compares the wicked to present experience, it's always tinder or weeds, never metal or stones in fire.
What conditionalists have done is take the biological death paradigm and applied it to the spirit paradigm. That is clearly an error and the foundational error upon which their whole system is erected.
What conditionalists have ACTUALLY done is noticed that God used human languages like Greek to speak to us, and we read what He actually says instead of making up unbiblical claims like "when He says death, he REALLY means separation" or "when He says destroy, He really means "make useless" and NOT "destroy." We conditionalists don't have to fight against our translations!