What does the “everlasting fire” mean?
1 But a doubt can arise as to the manner in which the devil, who has no body, and the souls of the damned before the resurrection, can suffer from the bodily fire by which the bodies of the damned will suffer in hell. As our Lord says: “Depart from Me you cursed into everlasting fire which was prepared for the devil and his angels” (Mat. 25:41).
2 One must not, then, judge the matter thus: that non-bodily substances can suffer from bodily fire so that their nature is corrupted by fire, or altered, or in any other way at all transmuted, as our corruptible bodies do now suffer by fire; because non-bodily substances have no bodily matter so as to be able to be changed by bodily things, and they are not even receptive to sensible forms except intelligibly—such reception, of course, is not proper to punishment, but tends, instead, to perfect and to please.
3 Neither can it be said that they suffer affliction from bodily fire by reason of any contrariety, as the bodies will suffer after the resurrection, because the non-bodily substances do not have organs of sense and do not use sense powers.
4 Therefore, the non-bodily substances suffer from bodily fire in the manner of a certain bondage. For spirits are able to be bound by bodies: this can be by way of form, as the soul is bound to the human body to give it life; or it can be without being the form of a something, as the necromancers by the power of devils bind spirits by images or that sort of thing. Therefore, much more can the divine power bind the spirits to be damned by bodily fire. And this is to them the greater affliction: they know they are in bondage to the lowliest things as a punishment.
5 It is also becoming that the damned spirits should be punished by bodily penalties. For the sin of every rational creature grows out of this: It is not subject to God in obedience. Punishment, of course, should answer to fault proportionally, with this result: that in its punishment the will suffer an affliction which is the contrary of that for whose love it sinned. Therefore, a befitting punishment to a sinning rational nature is this: to be subject somehow to the bondage of things which are its own inferiors, namely, bodily things.
6 Again, the sin committed against God deserves not only the punishment of loss, but the punishment of sense, as we showed in Book III, for the punishment of sense answers to the fault in regard to the soul’s disordered turning toward a changeable good, as the punishment of loss answers to the fault in regard to its taming away from the unchangeable good. But the rational creature, and especially the human soul, sins by its disordered taming to bodily things. Therefore, its becoming punishment is affliction by bodily things.
7 It furthermore, an afflicting punishment be due to sin, the one we call “the pain of sense,” such punishment ought to come from that which can bring on affliction. But nothing brings on affliction except so far as it is the contrary of the will. But it is not contrary to the natural will of a rational nature that it be united to a spiritual substance. Say, rather, this is a pleasure to it, and belongs to its perfection, for it is a union of like to like and of intelligible to intellect, since every spiritual substance is intelligible in itself. But it is contrary to the natural will of a spiritual substance to be in subjection to a body from which in the order of its own nature it ought to be free. It is, then, fitting to punish a spiritual substance with bodily things
8 In consequence, this, too, is clear: Grant that one understands the bodily aspects of the rewards of the blessed mentioned in Scripture spiritually, as was said about the promise of food and drink, nonetheless, when Scripture threatens certain bodily punishments to sinners, these are to be understood in a bodily fashion and taken in their own meaning. For there is nothing suitable about rewarding a superior nature by the use of an inferior one—the reward, rather, is in the union to the superior—but a superior nature is suitably punished by being turned over to its inferiors.
9 For all that, there is no reason why even some of the things we read in Scripture about the punishments of the damned expressed in bodily terms should not be understood in spiritual terms, and, as it were, figuratively.
Such is the saying of Isaiah (66:24): “Their worm shall not die”: by worm can be understood that remorse of conscience by which the impious will also be tortured, for a bodily worm cannot eat away a spiritual substance, nor even the bodies of the damned, which will be incorruptible.
Then, too, the “weeping” and “gnashing of teeth” (Mat. 8:12) cannot be understood of spiritual substances except metaphorically, although there is no reason not to accept them in a bodily sense in the bodies of the damned after the resurrection. For all that, this is not to understand weeping a loss of tears, for from those bodies there can be no loss, but there can be only the sorrow of the heart and the irritation of the eyes and the head which usually accompany weeping.