Objection 1: The punishment in Hell is infinite, and infinite punishment is unjust.Reply 1: Infinite means "without beginning or end." Hell is everlasting, meaning that it has no end, but it does have a beginning, so it is not infinite. The punishment also varies in intensity.
Objection 2: Hell is contrary to God's love.Reply 2: God is love, and love does not act coercively, but persuasively. Those who do not wish to be with God must be allowed to be separated from Him. Forgiveness must be freely given and freely accepted.
Objection 3: Hell has no redeeming value.Reply 3: Hell has redeeming value in that it "satisfies God's justice and glorifies it by showing how majestic and fearful a standard it is," according to Dr. Norman L. Geisler, Baker Encyclopedia of Christian Apologetics (Baker Academics: Grand Rapids, MI, 1999), 314.
Temporal Sins vs. Eternal Punishment
Objection 4: Sins are temporal in act, and so they do not deserve eternal punishment.Reply 4: Pope St. Gregory I the Great said that although sins are temporal in act, they are eternal in will, and so deserve eternal punishment. In the afterlife the mortal sinner never turns away from sin through a sincere conversion. Sin is also an offense against God’s infinite goodness, and thus is like infinite malice, which deserves eternal punishment.
Objection 5: The only just punishment is reformative/corrective. Everlasting damnation is not remedial or corrective to the damned and others and is therefore unjust.Reply 5: The punishment of the damned is for the correction of people presently on earth, and is not just intended to correct when being carried out, but also when it is decreed. God does everything in His power to reform people while they are still on earth, but cannot violate their free will. Justice demands that happiness must be deprived from one who leaves the right path on his search for happiness. Hell is only for the completely irreformable. At the same time, God would not extinguish souls because that is contrary to His perfect justice (see #7).
Accidental Nature of Punishment
Objection 6: Punishment is accidental and therefore cannot be everlasting.Reply 6: Punishment is related in essence to the guilty soul, and because guilt forever remains in the soul, its punishment will last forever.
Objection 7: The soul should be annihilated because the ungrateful deserve to lose all benefits, and a benefit from God to be lost is that of being/existence.Reply 7: Annihilation cannot be used to punish any sin because merit and demerit presuppose existence, and existence is not corrupted or ended by sin's inordinateness, according to St. Thomas Aquinas, Summa Theologica, Supp., q. 99, art. 1, ad 6 <http://www.newadvent.org/summa/5099.htm#article1>.
Objection 8: Hell means that God is not finally victorious over evil.Reply 8: On the contrary, there is no final victory over evil unless Hell exists because there needs to be an ultimate separation of good and evil in order for good to prevail. Hell is demanded by God's sovereignty.
Objection 9: Hell removes freedom of choice.Reply 9: People go to Heaven or Hell by their free will. Many people do not repent when warned of Hell, and so free choice is not removed. Some people are warned about the dangers of playing with fire, but they can still choose whether to play with fire.
Objection 10: The damned do not deserve bodily punishment by fire.Reply 10: Justice demands that punishment correspond to the gravity of sin. In sinning, the soul subjected itself to the body by its wicked desires. Thus it is just that the soul should be punished by being subjected to a bodily thing by suffering from it, according to St. Thomas Aquinas, Summa Theologica, Supp., q. 97, art. 5, resp. <http://www.newadvent.org/summa/5097.htm#article5>.