The argument has a simple structure: proportionality is a basic principle of justice. Punishment should fit the crime — the more serious the offence, the more severe the appropriate response. A finite life of wrongdoing — however serious — is a finite quantity of harm and wrongdoing. An infinite punishment for finite wrongdoing violates proportionality. A God who imposes such punishment is not just, regardless of the other attributes claimed for that God.
This is the proportionality objection to hell, and it is one of the strongest forms of the moral objection to orthodox religious accounts of damnation.
The duration objection and the nature objection
It helps to separate two versions of the objection. The first concerns duration: punishment that lasts forever is disproportionate to any finite crime. The second concerns nature: regardless of duration, a punishment of such severity as hell is traditionally described is disproportionate to anything a finite creature could do.
The duration objection has been engaged by the observation that the permanence of hell, in many classical accounts, is not primarily about accumulating proportionate punishment over infinite time. It is about the state of a being who has chosen, persistently and finally, to be the kind of thing that cannot abide the presence of goodness. The duration is not the punishment — it is the consequence of a choice that has become irreversible. The question of whether any choice can become truly irreversible is a different and important question, but it reframes the objection.
The infinite offence argument
Classical theistic responses to the proportionality objection — found in Aquinas and in Islamic theological literature — sometimes argue that the offence of rejecting God is not finite in the ordinary sense. God is infinite. A deliberate, fully-informed rejection of the infinite is not measured by the same scale as a finite harm to a finite person. This argument has some force but also an obvious weakness: it presupposes that the person making the choice did so with full information and full understanding, which most theological accounts of damnation do not require.
The honest position
The honest position is that the proportionality objection to traditional accounts of hell is serious and has not been fully answered within any tradition. It is one of the reasons that several serious theologians across traditions have moved toward conditional immortality (the annihilation rather than eternal torment of the damned), purgatorial accounts (suffering that is remedial rather than purely punitive), or universalism (eventual reconciliation of all).
The Islamic tradition contains more internal resources for engaging this question than is often acknowledged. The hadith traditions that describe God’s mercy as greater than God’s wrath, the Quranic insistence that God does not wrong anyone by so much as an atom’s weight, and the scholarly debates about the eventual end of hellfire — all of these are internal resources for approaching the proportionality question more seriously than a simple assertion of eternal torment would allow. The person who finds the proportionality objection compelling has found a genuine difficulty. They have also found a difficulty the tradition itself has not resolved simply or finally.