Thomas Aquinas

“ The form of a mixed body and the form of an element may be considered in two ways: either as regards the perfection of the species, and thus a mixed body is more perfect---or as regards their continual endurance; and thus the simple body is more noble, because it has not in itself the cause of corruption, unless it be corrupted by something extrinsic: whereas a mixed body has in itself the cause of its corruption, namely the composition of contraries. ”

“ The fire that will cleanse the elect before the judgment will be the same as the fire that will burn the world, although some say the contrary. For it is fitting that man, being a part of the world, be cleansed with the same fire as the world. They are, however, described as two fires, that will cleanse the good, and torture the wicked, both in reference to their respective offices, and somewhat in reference to their substance: since the substance of the cleansing fire will not all be cast into hell, as stated above. ”

“ In the elemental parts we must consider not only what is befitting a part considered in itself, but also what is befitting it in its relation to the whole. I say, then, that although water would be more noble if it had the form of fire, as likewise would earth and air, yet the universe would be more imperfect, if all elemental matter were to assume the form of fire. ”

“ For fire, whether produced by the sun or by some lower heating cause, is of the same species as fire in its own sphere, except in so far as the former has some admixture of foreign matter. And this will of necessity be the case then, since fire cannot cleanse a thing, unless this become its matter in some way. Hence we must grant that the fire in question is simply of the same species as ours. ”

“ The punishment of the wicked, even as the glory of the elect, will be greater after the judgment than before. Wherefore, just as charity will be added to the higher creature in order to increase the glory of the elect, so too whatever is vile in creatures will be thrust down into hell in order to add to the misery of the damned. Consequently it is not unbecoming that another fire be added to the fire of the damned that was prepared from the beginning of the world. ”

“ I answer that, Since the world was, in a way, made for man's sake, it follows that, when man shall be glorified in the body, the other bodies of the world shall also be changed to a better state, so that it is rendered a more fitting place for him and more pleasant to look upon. Now in order that man obtain the glory of the body, it behooves first of all those things to be removed which are opposed to glory. There are two, namely the corruption and stain of sin---because according to 1 Cor. ”

“ Further, fire does not cleanse except in so far as other things are made to be its matter. If, then, fire cleanses the other elements, they must needs become its matter. Therefore they must pass into its nature, and consequently be voided of their own nature. ”

“ When it is asserted that every creature of God is clean we are to understand this as meaning that its substance contains no alloy of evil, as the Manichees maintained, saying that evil and good are two substances in some places severed from one another, in others mingled together. ”

“ Further, in natural bodies those that are of the same species have the same movement. But that fire will have a different movement from the fire that is an element, because it will move in all directions so as to cleanse the whole. Therefore it is not of the same species.
On the contrary, Augustine says (De Civ. Dei xx, 16) , and his words are contained in a gloss on 1 Cor. 7:31, that "the fashion of this world will perish in the burning of worldly flames." Therefore that fire will be of the same nature as the fire which is now in the world. ”

“ The same answer applies to the Second Objection.
Reply to Objection 3: All men shall die and rise again: yet those are said to be found alive who will live in the body until the time of the conflagration. ”

“ Now in the higher heaven we find this indisposition both as regards guilt, since the devil sinned there, and as regards natural deficiency, since a gloss on Rom. 8:22, "We know that every creature groaneth and is in labor even until now," says: "All the elements fulfill their duty with labor: even as it is not without labor that the sun and moon travel their appointed course." Therefore the higher heavens also will be cleansed by that fire. ”

“ Although the bodies of the good will be reduced to ashes by the fire, they will not suffer pain thereby, as neither did the children in the Babylonian furnace. In this respect a distinction is drawn between the good and the wicked.
Reply to Objection 3: The elements that are in human bodies, even in the bodies of the elect, will be cleansed by fire. ”

“ Nor is there any thing that cannot in some way be cleansed by fire: some things, however, cannot be cleansed by fire without being destroyed themselves, such as cloths and wooden vessels, and these the Law ordered to be cleansed with water; yet all these things will be finally destroyed by fire. ”

“ But the second cleansing regards both the stain of sin and the impurity of mixture, and in respect of both it is more fitting for it to be effected by fire than by water. For the power of water tends to unite rather than to separate; wherefore the natural impurity of the elements could not be removed by water as by fire. Moreover, at the end of the world the prevalent sin will be that of tepidity, as though the world were already growing old, because then, according to Mat. ”

“ Moreover, these same elemental qualities belong to the second perfection of the elements, as being their proper passions: nor is it probable that in this final consummation the elements will lose anything of their natural perfection. ”

“ Now although, properly speaking, a corporeal thing cannot be the subject of the stain of sin, nevertheless, on account of sin corporeal things contract a certain unfittingness for being appointed to spiritual purposes ”