Objection 1: It would seem that not all the members of the human body will rise again. For if the end be done away it is useless to repair the means. Now the end of each member is its act. Since then nothing useless is done in the Divine works, and since the use of certain members is not fitting to man after the resurrection, especially the use of the genital members, for then they shall neither marry, nor he married (Matth. xxii. 30), it would seem that not all the members shall rise again.
Obj. 2: Further, The entrails are members: and yet they will not rise again. For they can neither rise full, since thus they contain impurities, nor empty, since nothing is empty in nature. Therefore the members shall not all rise again.
Obj. 3: Further, The body shall rise again that it may be rewarded for the works which the soul did through it. Now the member of which a thief has been deprived for theft, and who has afterwards done penance and is saved, cannot be rewarded at the resurrection, neither for any good deed, since it has not co-operated in any, nor for evil deeds, since the punishment of the member would redound to the punishment of the man. Therefore the members will not all rise again with man.
On the contrary, The other members belong more to the truth of human nature than hair and nails. Yet these will be restored to man at the resurrection according to the text (iv. Sent. D. 44). Much more therefore does this apply to the other members.
Further, The works of God are perfect (Deut. xxxii. 4). But the resurrection will be the work of God. Therefore man will be remade perfect in all his members.
I answer that, As stated in De Anima, ii., the soul stands in relation to the body not only as its form and end, but also as efficient cause. For the soul is compared to the body as art to the thing made by art, as the Philosopher says (Ethic. Magn. vii. 11), and whatever is shown forth explicitly in the product of art is all contained implicitly and originally in the art. In like manner whatever appears in the parts of the body is all contained originally and, in a way, implicitly in the soul. Thus just as the work of an art would not be perfect, if its product lacked any of the things contained in the art, so neither could man be perfect, unless the whole that is contained enfolded in the soul be outwardly unfolded in the body, nor would the body correspond in full proportion to the soul. Since then at the resurrection it behoves man's body to correspond entirely to the soul, for it will not rise again except according to the relation it bears to the rational soul, it follows that man also must rise again perfect, seeing that he is thereby repaired in order that he may obtain his ultimate perfection. Consequently all the members that are now in man's body must needs be restored at the resurrection.
Reply Obj. 1: The members may be considered in two ways in relation to the soul: either according to the relation of matter to form, or according to the relation of instrument to agent, since the whole body is compared to the whole soul in the same way as one part is to another [De Anima, ii., text. 9). If then the members be considered in the light of the first relationship, their end is not operation, but rather the perfect being of the species, and this is also required after the resurrection: but if they be considered in the light of the second relationship, then their end is operation. And yet it does not follow that when the operation fails the instrument is useless, because an instrument serves not only to accomplish the operation of the agent, but also to show its virtue. Hence it will be necessary for the virtue of the soul's powers to be shown in their bodily instruments, even though they never proceed to action, so that the wisdom of God be thereby glorified.
Reply Obj. 2: The entrails will rise again in the body even as the other members: and they will be filled not with vile superfluities but with goodly humours.
Reply Obj. 3: The acts whereby we merit are not the acts, properly speaking, of hand or foot but of the whole man; even as the work of art is ascribed not to the instrument but to the craftsman. Therefore though the member which was cut off before a man's repentance did not co-operate with him in the state wherein he merits glory, yet man himself merits that the whole man may be rewarded, who with his whole being serves God.
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