If hell were not eternal, it would not be so frightful a chastisement. Thomas a Kempis says, that “everything which passes with time is trifling and short.” Any pain which has an end is not very appalling. The man who labors under an imposthume or a cancer, must submit to the knife or the cautery: the pain is severe; but because it is soon over it can be borne. But a toothache which lasts for three months without interruption is insupportable. Were a person obliged to lie in the same posture for six months on a soft bed, or even to hear the same music, or the same comedy, night and day for one year, he would fall into melancholy and despondency. Poor blind sinners! When threatened with hell they say:” If I go there, I must have patience.” But they shall not say so when they will have entered that region of woes, where they must suffer, not by listening to the same music or the same comedy, nor by lying in the same posture, or by toothache, but by enduring all torments and all evils.” I will heap evils upon them.” (Deut. xxxiii. 23.) And all these torments shall never end.
form a sermon of Saint Alphonsus Liguori – on ‘the Eternity of Hell’