“Eternal Punishment” is the term used in the English translation of the Bible on which most people base their view of eternal conscious torment in Hell. The term in the Greek is “kolasis aionios.” If this term does indeed mean eternal punishment, then hell would seem to be foreverrrrrrrrrr.
But, such is not the case. Let’s first consider the opinion of the great Greek scholar William Barclay, who was professor of Divinity and Biblical Criticism at Glasgow University and the author of many commentaries and books, including a translation of the New Testament and the very popular Daily Study Bible Series. Barclay discusses this point regarding Matthew 25:46 in his well-known autobiography:
“One of the key passages is Matthew 25:46 where it is said that the rejected go away to eternal punishment, and the righteous to eternal life. The Greek word for punishment is ‘kolasis,’ which was not originally an ethical word at all. It originally meant the pruning of trees to make them grow better. I think it is true to say that in all Greek secular literature ‘kolasis’ is never used of anything but ‘remedial punishment.’ The word for ‘eternal’ is aionios. It means more than everlasting, for Plato - who may have invented the word - plainly says that a thing may be everlasting and still not be aionios. The simplest way to put it is that aionios cannot be used properly of anyone but God; it is the word uniquely, as Plato saw it, of God. Eternal punishment is then literally that kind of remedial punishment which it befits God to give and which only God can give.”
Aristotle supports Barclay on the meaning of "kolasis."
The only word in the Gospels for “punishment” with regard to God punishing evildoers is “kolasis,” which according to Aristotle, who knew Greek word meanings better than anybody who ever walked the planet, said that “kolasis” is the kind of punishment which “is inflicted in the interest of the sufferer,” which means it is for the betterment or improvement of the person being punished.
This is contrasted with “timoria,” which Aristotle said is the kind of punishment which is “inflicted in the interest of him who inflicts it, that he may obtain satisfaction.” (Rhet. 1369b13).
In addition to Barclay’s opinion above, let’s consider some other respected sources about the proper translation of “aionios:"
The Rotterham Emphasized Bible translates “kolasis aionios” in Matthew 25:46 as “age abiding correction.”
Young’s Literal Translation translates “kolasis aionios” in Matthew 25:46 as “punishment age.”
The Concordant Literal Translation translates “kolasis aionios” in Matthew 25:46 as “chastening eonian," or “chastening age” in other words. Our English word “eon” derives from the Greek word “aionios.” Eon, as we use the word, speaks of ages or cycles of indeterminate amounts of time. The term is often used in the plural form, such as “It’s been eons since we’ve talked,” or “Eons ago the universe was formed.” The point is that we don’t even use the term today to refer to “everlasting” in the sense of never ending. Think how silly it sounds to pluralize “everlasting” into “everlastings," yet “eon” is pluralized into “eons” all the time.
The best translators of the New Testament Greek text would be the Greek fathers of the church over the first 500 years. They were Christian. They were scholars. They lived nearest to the time the New Testament was written and would have a better grasp of the grammatical nuances and cultural linguistics of recent generations. Koine Greek was a lost language for hundreds of years and it is somewhat presumptuous for modern scholars to think they know Biblical Greek better than did the Greek-speaking Church fathers.
The Church fathers and writers who used the term “aionios” in their writings to refer to an indefinite “age” and not to an “unending” or “everlasting” eternity are: Ignatius, Justin Martyr, Irenaeus, Hermogones, Origen, Eusebius, Gregory of Nyssa, and Avitus.
“Eternity (Greek Aionios) signifies in Scripture sometimes the fact that we do not know the end, sometimes the fact that there is no end in the present world, but there will be one in the next. Sometimes eternity means a certain length of time, even that of a human life.” (Origen, Commentary on Romans, Book 6, section 5).
The Emperor Justinian in A.D. 540 tried to extinguish Origen’s teachings by defining Catholic doctrine at that time. “The Holy Church of Christ teaches an endless aionios (ATELEUTETOS aionios) life to the righteous, and endless (ateleutetos) punishment to the wicked.” Aionios was not enough in his judgment to denote endless duration, so he employed ateleutetos. The point is that “aionios” by itself did not mean “everlasting.” It needed to be strengthened with another word to in fact mean “endless,” like “ateleutetos.”
Jews who were contemporaries with Christ, but who wrote in Greek, show that “aionios” was not used to mean “everlasting.” Josephus the historian used “aionios” to refer to temples which were already destroyed (and thus not “everlasting”), indeterminate prison sentences and time lapses between historical events. He never used the word to denote “everlasting,” but rather to mean an indeterminate period or season. The Jewish writer Philo always used the words athanaton, ateleuteton or aidion to denote endless and aionion for temporary duration.
Augustine, who struggled mightily with Greek, claimed for years that the only meaning of “aionios” was “everlasting,” yet even he had to acknowledge his error when visited by the Spanish presbyter Orosius, who convinced Augustine of his error. Augustine relented, but only to the extent that “aionios” did not only mean “everlasting.” Augustine still believed it means “everlasting” with regard to Hell.
To summarize then, Greek word “Aionios,” which is sometimes translated as “everlasting” in Scripture (as in “everlasting punishment”), does NOT in fact mean "unending or everlasting in quantity of time."
Rather, “Aionios” speaks to an “indeterminate age set by God alone.” The word refers to a certain quality (not quantity) of being - - whether it be “aionios life” or “aionios remedial-punishment.” Aionios is always qualified by what it is describing.
For instance, the word “great,” when applied to a merciful sentence imposed by a kind-hearted judge, might refer to a small amount of time in jail. Conversely, “great,” when applied to an atrocious crime, for which the judge “throws the book” at the defendant, might refer to a life-sentence in jail.
Similarly, the nature and quality of aionios, applied to the life of God, is entirely different than when it is applied to the chastening or punishment of God. “GREAT life” in God is certainly unending, since death will have been completely defeated, but the unending length is not the primary essence of that “GREAT life.” Rather, the limitless quality of love and peace which come from being totally at one with the Lord is the key aspect of this “GREAT life.” On the other hand, “GREAT punishment” by God will not be unending since He punishes to correct and rehabilitate and He is not willing that any should perish, but that all should come to repentance. 2 Pet. 3:9.
Life in God is not everlasting because it is aionios, but rather aionios is everlasting because it is referring to life in God.
Conversely, aionios punishment is not temporary because aionios means temporary, but rather aionios is temporary in this context since God’s chastening is curative and incapable of being eternally resisted. “For his anger is but for a moment; His favor is for a life-time: Weeping may tarry for the night, But joy ‘cometh’ in the morning.” Psalm 30:5.
Aionios then, by itself, means an “indeterminate age,” not an “unending age.” Only the context of the passage provides guidance as to the actual quality and duration of the age.