1. It teaches, first, that the resurrection is not a mere accidental glory, which may or may not be given to the just, but that it is an essential element of man's happiness.* The soul of Abraham, for instance, that is now united to God in the Beatific Vision, is not, properly speaking, Abraham himself, but only a part of him. In order, therefore, to be perfect according to her nature, that soul must again be clothed with her own body of real flesh and blood, so that Abraham may again be a living man, and that God may be called, in the fullest sense of the word, "the God of the living." Evidently the same must be said of every other soul now basking in the light of God's countenance.
* Anima corpori naturaliter unitur; est enim secundum suam essentiam corporis forma; est igitur contra naturam animaæ absque corpore esse. Nihil autem quod est contra naturam potest esse perpetuum ... oportet eam (animam) corpori iterato conjungi, quod est resurgere. Sum. contr. gent., lib. 4, cap. 79. .... Ad secundum, dicendum quod anima Abrahæ non est proprie loquendo ipso Abraham, sed pars eius, et sic de aliis. Unde vita animæ Abrahæ non sufficeret ad hoc quod Abraham sit vivens, vel quod Deus Abraham sit Deus viventis: sed exigitur vita totius conjuncti, scilicet animæ et corporis, quæ quidem vita quamvis non esset in actu, quando verba proponebantur, erat tamen in ordine utriusque partis ad resurrectionem: unde Dominus per verba illa subtilissime et efficaciter resurrectionem profit.--S. Thom., Suppl., q. 75, art. 1.
We are not angels, but men. An angel is a superior being, and of a different order from us. He is a spirit, and complete as such without a body. But the human soul, although a spirit too, is not perfect without a body; for, as such, she is only a part of the being called man. Besides, it is not the soul alone that is to enjoy the happiness of heaven; it is man. And as he is composed of both soul and body, it is necessary that the soul should again be clothed with her body, so that man may be placed in the enjoyment of heaven's happiness in his whole being.
2. Theology teaches, in the second place, that the happiness of the blessed is increased by the resurrection, because the soul is enabled to receive new pleasures by her reunion with a glorified body. And, first, the human soul, which is not only intellectual, but also sensitive, receives those organs by which she is again enabled to exercise her imagination, and other faculties of her emotional or sensitive nature; all of which are sources of great enjoyment. Secondly, by her reunion with the body, she is again empowered to receive pleasure through the glorified senses. Thirdly, the soul is made more perfect in all her operations by her reunion with a glorified body.* The human body as now constituted, or rather as injured by sin, does not, it is true, always perfect the soul in her operations; it rather impedes her, at hast in many of them. Hence, the Wise Man tells us that "The corruptible body is a load upon the soul, and the earthly habitation presseth down the mind that museth many things."+ If therefore, a glorified soul were reunited to such a body, undoubtedly her operations would not be made more perfect than they are in her separate state. But it is not to be so. The soul is to be reunited to a glorified body, that will be entirely subject to the spirit, and will, in consequence, perfect all its intellectual operations, its moral affections, and every other act which, according to its nature, it can perform.