Thomas Aquinas, Compendium of Theology

Although men will rise as the same individuals, they will not have the same kind of life as before. Now their life is corruptible; then it will be incorruptible. If nature aims at perpetual existence in the generation of man, much more so does God in the restoration of man. Nature's tendency toward never-ending existence comes from an impulse implanted by God. The perpetual existence of the species is not in question in the restoration of risen man, for this could be procured by repeated generation. Therefore what is intended is the perpetual existence of the individual. Accordingly risen men will live forever.

Besides, if men once risen were to die, the souls separated from their bodies would not remain forever deprived of the body, for this would be against the nature of the soul, as we said above. Therefore they would have to rise again; and the same thing would happen if they were to die again after the second resurrection. Thus death and life would revolve around each man in cycles of infinite succession; which seems futile. Surely a halt is better called at the initial stage, so that men might rise to immortal life at the first resurrection.

However, the conquest of mortality will not induce any diversity either in species or in number. The idea of mortality contains nothing that could make it a specific difference of man, since it signifies no more than a passion. It is used to serve as a specific difference of man in the sense that the nature of man is designated by calling him mortal, to bring out the fact that he is composed of contrary elements, just as his proper form is designated by the predicate "rational"; material things cannot be defined without including matter. However, mortality is not overcome by taking away man's proper matter. For the soul will not resume a celestial or ethereal body, as was mentioned above; it will resume a human body made up of contrary elements. Incorruptibility will come as an effect of divine power, whereby the soul will gain dominion over the body to the point that the body cannot corrupt. For a thing continues in being as long as form has dominion over matter.