Objection 1. It would seem that by reason of this subtlety a body is able to be in the same place with another body not glorified. For according to Philippians 3:21, "He will reform the body of our lowness made like to the body of His glory." Now the body of Christ was able to be in the same place with another body, as appears from the fact that after His Resurrection He went in to His disciples, the doors being shut (John 20:19-26). Therefore also the glorified bodies by reason of their subtlety will be able to be in the same place with other bodies not glorified.
Objection 2. Further, glorified bodies will be superior to all other bodies. Yet by reason of their superiority certain bodies, to wit the solar rays, are able now to occupy the same place together with other bodies. Much more therefore is this befitting glorified bodies.
Objection 3. Further, a heavenly body cannot be severed, at least as regards the substance of the spheres: hence it is written (Job 37:18) that "the heavens... are most strong, as if they were of molten brass." If then the subtlety of a glorified body will not enable it to be in the same place together with another body, it will never be able to ascend to the empyrean,* and this is erroneous. [The empyrean was the highest of the concentric spheres or heavens, and was identified by Christian writers with the abode of God. Cf. I, 56, 3].
Objection 4. Further, a body which is unable to be in the same place with another body can be hindered in its movement or even surrounded by others standing in its way. But this cannot happen to glorified bodies. Therefore they will be able to be together in the same place with other bodies.
Objection 5. Further, as point is to point, so is line to line, surface to surface, and body to body. Now two points can be coincident, as in the case of two lines touching one another, and two lines when two surfaces are in contact with one another, and two surfaces when two bodies touch one another, because "contiguous things are those whose boundaries coincide" (Phys. vi, 6). Therefore it is not against the nature of a body to be in the same place together with another body. Now whatever excellence is competent to the nature of a body will all be bestowed on the glorified body. Therefore a glorified body, by reason of its subtlety, will be able to be in the same place together with another body.
On the contrary, Boethius says (De Trin. i): "Difference of accidents makes distinction in number. For three men differ not in genus, nor in species, but in their accidents. If we were to remove absolutely every accident from them, still each one has a different place; and it is quite conceivable that they should all occupy the same place." Therefore if we suppose two bodies to occupy the same place, there will be but one body numerically.
I answer that, It cannot be maintained that a glorified body, by reason of its subtlety, is able to be in the same place with another body, unless the obstacle to its being now in the same place with another body be removed by that subtlety. Some say that in the present state this obstacle is its grossness by virtue of which it is able to occupy a place; and that this grossness is removed by the gift of subtlety. But there are two reasons why this cannot be maintained. First, because the grossness which the gift of subtlety removes is a kind of defect, for instance an inordinateness of matter in not being perfectly subject to its form. For all that pertains to the integrity of the body will rise again in the body, both as regards the matter and as regards the form. And the fact that a body is able to fill a place belongs to it by reason of that which pertains to its integrity, and not on account of any defect of nature. For since fulness is opposed to vacancy, that alone does not fill a place, which being put in a place, nevertheless leaves a place vacant. Now a vacuum is defined by the Philosopher (Phys. iv, 6,7) as being "a place not filled by a sensible body." And a body is said to be sensible by reason of its matter, form, and natural accidents, all of which pertain to the integrity of nature. It is also plain that the glorified body will be sensible even to touch, as evidenced by the body of our Lord (Luke 24:39): nor will it lack matter, or form, or natural accidents, namely heat, cold, and so forth. Hence it is evident that the glorified body, the gift of subtlety notwithstanding, will fill a place: for it would seem madness to say that the place in which there will be a glorified body will be empty. Secondly their aforesaid argument does not avail, because to hinder the co-existence of a body in the same place is more than to fill a place. For if we suppose dimensions separate from matter, those dimensions do not fill a place. Hence some who held the possibility of a vacuum, said that a vacuum is a place wherein such like dimensions exist apart from a sensible body; and yet those dimensions hinder another body from being together with them in the same place. This is made clear by the Philosopher (Phys. iv, 1,8; Metaph. ii, 2), where he considers it impossible for a mathematical body, which is nothing but separate dimensions, to be together with another natural sensible body. Consequently, granted that the subtlety of a glorified body hindered it from filling a place, nevertheless it would not follow that for this reason it is able to be in the same place with another body, since the removal of the lesser does not involve the removal of the greater.
Accordingly we must say that the obstacle to our body's being now in the same place with another body can nowise be removed by the gift of subtlety. For nothing can prevent a body from occupying the same place together with another body, except something in it that requires a different place: since nothing is an obstacle to identity, save that which is a cause of distinction. Now this distinction of place is not required by any quality of the body, because a body demands a place, not by reason of its quality: wherefore if we remove from a body the fact of its being hot or cold, heavy or light, it still retains the necessity of the aforesaid distinction, as the Philosopher proves (Phys. iv), and as is self-evident. In like manner neither can matter cause the necessity of the aforesaid distinction, because matter does not occupy a place except through its dimensive quantity. Again neither does form occupy a place, unless it have a place through its matter. It remains therefore that the necessity for two bodies occupying each a distinct place results from the nature of dimensive quantity, to which a place is essentially befitting. For this forms part of its definition, since dimensive quantity is quantity occupying a place. Hence it is that if we remove all else in a thing from it, the necessity of this distinction is found in its dimensive quantity alone. Thus take the example of a separate line, supposing there to be two such lines, or two parts of one line, they must needs occupy distinct places, else one line added to another would not make something greater, and this is against common sense. The same applies to surfaces and mathematical bodies. And since matter demands place, through being the subject of dimension, the aforesaid necessity results in placed matter, so that just as it is impossible for there to be two lines, or two parts of a line, unless they occupy distinct places, so is it impossible for there to be two matters, or two parts of matter, without there be distinction of place. And since distinction of matter is the principle of the distinction between individuals, it follows that, as Boethius says (De Trin.), "we cannot possibly conceive two bodies occupying one place," so that this distinction of individuals requires this difference of accidents. Now subtlety does not deprive the glorified body of its dimension; wherefore it nowise removes from it the aforesaid necessity of occupying a distinct place from another body. Therefore the subtlety of a glorified body will not enable it to be in the same place together with another body, but it will be possible for it to be together with another body by the operation of the Divine power: even as the body of Peter had the power whereby the sick were healed at the passing of Peter's shadow (Acts 5:15) not through any inherent property, but by the power of God for the upbuilding of the faith. Thus will the Divine power make it possible for a glorified body to be in the same place together with another body for the perfection of glory.
Reply to Objection 1. That Christ's body was able to be together with another body in the same place was not due to its subtlety, but resulted from the power of His Godhead after His resurrection, even as in His birth [Cf. III, 28, 2, ad 3]. Hence Gregory says (Hom. xxvi in Evang.): "The same body went into His disciples the doors being shut, which to human eyes came from the closed womb of the Virgin at His birth." Therefore there is no reason why this should be befitting to glorified bodies on account of their subtlety.
Reply to Objection 2. Light is not a body as we have said above (Sent. ii, 13, 3; I, 67, 2): hence the objection proceeds on a false supposition.
Reply to Objection 3. The glorified body will pass through the heavenly spheres without severing them, not by virtue of its subtlety, but by the Divine power, which will assist them in all things at will.
Reply to Objection 4. From the fact that God will come to the aid of the blessed at will in whatever they desire, it follows that they cannot be surrounded or imprisoned.
Reply to Objection 5. As stated in Phys. iv, 5, "a point is not in a place": hence if it be said to be in a place, this is only accidental, because the body of which it is a term is in a place. And just as the whole place corresponds to the whole body, so the term of the place corresponds to the term of the body. But it happens that two places have one term, even as two lines terminate in one point. And consequently though two bodies must needs be in distinct places, yet the same term of two places corresponds to the two terms of the two bodies. It is in this sense that the bounds of contiguous bodies are said to coincide.
Source: Summa Theologica (New Advent)