Thomas Aquinas, Compendium of Theology

We should realize that the happiness enjoyed by the souls of the saints will consist exclusively in spiritual goods. On the other hand, the punishment inflicted on the souls of the damned, even before the resurrection, will not consist solely in spiritual evils, as some have thought; lost souls will also undergo corporal punishment.

The reason for this difference is as follows. When the souls of the saints were united to their bodies here in this world, they observed right order, not subjecting themselves to material things but serving God alone. And so their whole happiness consists in the enjoyment of Him, not in any material goods. But the souls of the wicked, in violation of the order of nature, set their affections on material things, scorning divine and spiritual goods. In consequence, they are punished not only by being deprived of spiritual goods, but by being subjected to the tyranny of material things. Accordingly, if Sacred Scripture is found to promise a reward of material goods to the souls of the saints, such passages are to be interpreted in a mystical sense; for spiritual things are often described in Scripture in terms of their likeness to material things. But texts that portend the corporal punishments of the souls of the damned, specifying that they will be tormented by the fires of hell, are to be understood literally.