That was Augustine's spurious, simplistic argument. He was quite ignorant of the Greek language. Consider, for example, the following:
More literal translations of the Greek word aionion in Mt.25:46 say:
Concordant Literal New Testament, 1983
And these shall be coming away into chastening eonian, yet the just into life eonian."
The New Testament: A Translation, by Eastern Orthodox scholar David Bentley Hart, 2017, Yale Press):"And these shall go to the chastening of that Age, but the just to the life of that Age."
Emphatic Diaglott, 1942 edition
"And these shall go forth to the aionian 1 cutting-off; but the RIGHTEOUS to aionian Life."
There are two main universalist interpretations of Mt.25:46:
(1) The aionion life & the aionion punishment refer to contrasting eonian destinies pertaining to a finite eonian period to come, e.g. the millennial eon. The verse has nothing to do, & says nothing about, final destiny. Regarding the endless life of the righteous in Christ, other passages address that topic, such as those that speak of immortality, incorruption & being unable to die.
(2) Another universalist option in interpretating Mt.25:46 is that aionion life refers to a perpetual life that lasts as long as God Almighty wills it to last, so it is endless. OTOH, aionion punishment refers to a perpetual punishment that also lasts as long as Love Omnipotent wills it to last, which is until it has served its useful purpose in bringing the offender to the salvation in their Savior, Who died & shed His blood for their sins. While life is an end in itself, punishment is a means to an end.
Furthermore, since aionion is an adjective, it "must therefore function like an adjective, and it is the very nature of an adjective for its meaning to vary, sometimes greatly, depending upon which noun it qualifies." A tall chair is not the same height as a tall mountain. Likewise, the aionion punishment is not of the same duration as the aionion life.
That was a brief explanation of the main two different universalist interpretations of Mt.25:46. Following are more elaborate remarks in support these two perspectives:
Is aionion necessarily coequal in duration with aionion (in Mt.25:46)?
For further reading re Matthew 25:46:
Augustine's ignorance & error re Matthew 25:46
City-Data Forum - View Single Post - What does Matthew 25:46 mean?
What does Matthew 25:46 mean? (Gomorrah, Gospel, unpardonable, hell) - Christianity - - City-Data Forum
Have you been decieved by your Bible translation?
An argument for "eternal conscious torment"
Matthew 25:46 paralllel argument with Rom 5 19:
Universalist Understanding?
Easy to say. Another thing to prove. Can you prove the "aionion" fire (Jude 1:7) that burned Sodom burned forever? Is Sodom still burning? If that fire was temporary & not "eternal", why must the use of the same words, aionion fire, in Matthew 18:8 & 25:41 mean the fire is "eternal"? Is Love Omnipotent an eternal sadist infinitely worse than what Satan, Hitler & Stalin have done combined?
Words have various meanings depending upon their context. In ancient Koine Greek, which includes the New Testament and Greek Old Testament, aionios refers - at least sometimes - if not often - to a finite duration, not eternal duration. Many scholars admit that the Greek word aionios is used of age lasting and/or finite duration . Even more scholars recognize that fact. The fact is the word aionios can refer to a finite duration. For example:
In the Greek Old Testament (LXX, Septuagint) of Isaiah 54:4 the word aionios appears and is used of finite duration:
4 You should not fear that you were disgraced, nor should you feel ashamed that you were berated. For shame everlasting(aionios) you shall forget; and the scorn of your widowhood in no way shall you remember any longer (Apostolic Bible Polygot, LXX)
The same phrase, and Greek words, for "shame everlasting"(aionios) in Isa.54:4 occur again at Dan.12:2 LXX, which i have higlighted within the brackets:
Dan.12:2 καὶ πολλοὶ τῶν καθευδόντων ἐν γῆς χώματι ἐξεγερθήσονται οὗτοι εἰς ζωὴν αἰώνιον καὶ οὗτοι εἰς ὀνειδισμὸν καὶ εἰς [αἰσχύνην αἰώνιον]
Isa.54:4 μὴ φοβοῦ ὅτι κατῃσχύνθης μηδὲ ἐντραπῇς ὅτι ὠνειδίσθης ὅτι [αἰσχύνην αἰώνιον] ἐπιλήσῃ καὶ ὄνειδος τῆς χηρείας σου οὐ μὴ μνησθήσῃ
Kata Biblon Wiki Lexicon - ??????? - shame/disgrace/dishonor (n.)
Strong's Greek: 152. ??????? (aischuné) -- shame
In Isa.54:4 aionios/eonian is finite: "For shame everlasting[eonian] you shall forget".
The same Greek word for "eternal", i.e. aionios, is also used by early church father Chrysostom of an obviously finite duration here:
"For that his[Satan's] kingdom is of this age,[αἰώνιος] i.e., will cease with the present age[αιώνι] ..." (Homily 4 on Ephesians, Chapter II. Verses 1-3).
CHURCH FATHERS: Homily 4 on Ephesians (Chrysostom)
The Greek text may be found here:
http://www.documentacatholicaomnia...._In_epistulam_II_ad_Thessalonicenses,_MGR.pdf
In Philo is another example of aionios:
""Philo [20 BC - 50 AD, contemporary with Christ] used the exact phraseology we find in Matthew 25:46 - just as Christ used it - in the context of temporal affairs between people of different socio-economic classes:"
" "It is better not to promise than not to give prompt assistance, for no blame follows in the former case, but in the latter there is dissatisfaction from the weaker class, and a deep hatred and everlasting punishment (kolasis aiónios) from such as are more powerful" (Fragmenta, Tom. ii., p. 667)."
That Happy Expectation: Eternal or Eonian? Part Five (The Greek Adjective Aiónios)
"It is better absolutely never to make any promise at all than not to assist another willingly, for no blame attaches to the one, but great dislike on the part of those who are less powerful, and intense hatred and long enduring punishment from those who are more powerful, is the result of the other line of conduct."
Philo: Appendix 2: Fragments
" "It is better not to promise than not to give prompt assistance, for no blame follows in the former case, but in the latter there is dissatisfaction from the weaker class, and a deep hatred and everlasting punishment [kolasis aiónios] from such as are more powerful." Here we have the exact terms employed by out Lord, to show that aiónion did not mean endless but did mean limited duration in the time of Christ."
Kolasis
"In the Apostolical Constitutions, a work of the fourth century A.D., it is said, kai touto humin esto nomimon aionion hos tes suntleias to aionos, "And let this be to you an eonian ordinance until the consummation of the eon." Obviously there was no thought in the author's mind of endless time...."
More examples of aionios as a finite duration in Koine Greek:
Two Questions
Does aionios always mean eternal in ancient Koine Greek? (paradise, Gospel, hell) - Christianity - - City-Data Forum
If Jesus wished to express endless punishment, then He would have used expressions such as "endless", "no end" & "never be saved" as per:
How Scripture expresses endless duration (not aion/ios) (paradise, hell, punishment) - Christianity - - City-Data Forum
Jesus didn't use the best words & expressions to describe endlessness in regards to punishment, because He didn't believe in endless punishment.
ENDLESSNESS not applied to eschatological PUNISHMENT in Scripture:
could an 'eternal punishment' simply mean that once instituted it will not change?
12 points re forever and ever (literally to/into "the ages of the ages") being finite:
For the Lord will NOT cast off FOR EVER: