They who are of this opinion would have all punishments after death to be purgatorial; and as the elements of air, fire, and water are superior to earth, one or other of these may be the instrument of expiating and purging away the stain contracted by the contagion of earth. So Virgil hints at the air in the words, "Some hang aloft for winds to pierce;" at the water in "whelming tide;" and at fire in the expression "in burning fire." For our part, we recognize that even in this life some punishments are purgatorial — not, indeed, to those whose life is none the better, but rather the worse for them, but to those who are constrained by them to amend their life. All other punishments, whether temporal or eternal, inflicted as they are on every one by divine providence, are sent either on account of past sins, or of sins presently allowed in the life, or to exercise and reveal a man's graces. They may be inflicted by the instrumentality of bad men and angels as well as of the good. For even if any one suffers some hurt through another's wickedness or mistake, the man indeed sins whose ignorance or injustice does the harm; but God, who by His just though hidden judgment permits it to be done, sins not. But temporary punishments are suffered by some in this life only, by others after death, by others both now and then; but all of them before that last and strictest judgment. But of those who suffer temporary punishments after death, all are not doomed to those everlasting pains which are to follow that judgment; for to some, as we have already said, what is not remitted in this world is remitted in the next, that is, they are not punished with the eternal punishment of the world to come.

From Augustine's City of God