Objection 1. It would seem that the souls in heaven or hell are unable to go from thence. For Augustine says (De Cura pro Mort. xiii): "If the souls of the dead took any part in the affairs of the living, to say nothing of others, there is myself whom not for a single night would my loving mother fail to visit since she followed me by land and sea in order to abide with me": and from this he concludes that the souls of the departed do not mingle in the affairs of the living. But they would be able to do so if they were to leave their abode. Therefore they do not go forth from their abode.
Objection 2. Further, it is written (Psalm 26:4): "That I may dwell in the house of the Lord all the days of my life," and (Job 7:9): "He that shall go down to hell shall not come up." Therefore neither the good nor the wicked quit their abode.
Objection 3. Further, as stated above (Article 2), abodes are awarded to souls after death as a reward or punishment. Now after death neither the rewards of the saints nor the punishments of the damned are increased. Therefore they do not quit their abodes.
On the contrary, Jerome writing against Vigilantius addresses him thus: "For thou sayest that the souls of the apostles and martyrs have taken up their abode either in Abraham's bosom or in the place of refreshment, or under the altar of God, and that they are unable to visit their graves when they will. Wouldst thou then lay down the law for God? Wouldst thou put the apostles in chains, imprison them until the day of judgment, and forbid them to be with their lord, them of whom it is written: They follow the Lamb whithersoever He goeth? And if the Lamb is everywhere, therefore we must believe that those also who are with Him are everywhere." Therefore it is absurd to say that the souls of the departed do not leave their abode.
Further, Jerome argues as follows: "Since the devil and the demons wander throughout the whole world, and are everywhere present with wondrous speed, why should the martyrs, after shedding their blood be imprisoned and unable to go forth?" Hence we may infer that not only the good sometimes leave their abode, but also the wicked, since their damnation does not exceed that of the demons who wander about everywhere.
Further, the same conclusion may be gathered from Gregory (Dial. iv), where he relates many cases of the dead having appeared to the living.
I answer that, There are two ways of understanding a person to leave hell or heaven. First, that he goes from thence simply, so that heaven or hell be no longer his place: and in this way no one who is finally consigned to hell or heaven can go from thence, as we shall state further on (71, 5, ad 5). Secondly, they may be understood to go forth for a time: and here we must distinguish what befits them according to the order of nature, and what according to the order of Divine providence; for as Augustine says (De Cura pro Mort. xvi): "Human affairs have their limits other than have the wonders of the Divine power, nature's works differ from those which are done miraculously." Consequently, according to the natural course, the separated souls consigned to their respective abodes are utterly cut off from communication with the living. For according to the course of nature men living in mortal bodies are not immediately united to separate substances, since their entire knowledge arises from the senses: nor would it be fitting for them to leave their abode for any purpose other than to take part in the affairs of the living. Nevertheless, according to the disposition of Divine providence separated souls sometimes come forth from their abode and appear to men, as Augustine, in the book quoted above, relates of the martyr Felix who appeared visibly to the people of Nola when they were besieged by the barbarians. It is also credible that this may occur sometimes to the damned, and that for man's instruction and intimidation they be permitted to appear to the living; or again in order to seek our suffrages, as to those who are detained in purgatory, as evidenced by many instances related in the fourth book of the Dialogues. There is, however, this difference between the saints and the damned, that the saints can appear when they will to the living, but not the damned; for even as the saints while living in the flesh are able by the gifts of gratuitous grace to heal and work wonders, which can only be done miraculously by the Divine power, and cannot be done by those who lack this gift, so it is not unfitting for the souls of the saints to be endowed with a power in virtue of their glory, so that they are able to appear wondrously to the living, when they will: while others are unable to do so unless they be sometimes permitted.
Reply to Objection 1. Augustine, as may be gathered from what he says afterwards, is speaking according to the common course of nature, And yet it does not follow, although the dead be able to appear to the living as they will, that they appear as often as when living in the flesh: because when they are separated from the flesh, they are either wholly conformed to the divine will, so that they may do nothing but what they see to be agreeable with the Divine disposition, or else they are so overwhelmed by their punishments that their grief for their unhappiness surpasses their desire to appear to others.
Reply to Objection 2. The authorities quoted speak in the sense that no one comes forth from heaven or hell simply, and do not imply that one may not come forth for a time.
Reply to Objection 3. As stated above (1, ad 3) the soul's place conduces to its punishment or reward in so far as the soul, through being consigned to that place, is affected either by joy or by grief. Now this joy or grief at being consigned to such a place remains in the soul even when it is outside that place. Thus a bishop who is given the honor of sitting on a throne in the church incurs no dishonor when he leaves the throne, for though he sits not therein actually, the place remains assigned to him.
We must also reply to the arguments in the contrary sense.
Reply to Objection 4. Jerome is speaking of the apostles and martyrs in reference to that which they gain from their power of glory, and not to that which befits them as due to them by nature. And when he says that they are everywhere, he does not mean that they are in several places or everywhere at once, but that they can be wherever they will.
Reply to Objection 5. There is no parity between demons and angels on the one hand and the souls of the saints and of the damned on the other. For the good or bad angels have allotted to them the office of presiding over men, to watch over them or to try them; but this cannot be said of the souls of men. Nevertheless, according to the power of glory, it is competent to the souls of the saints that they can be where they will; and this is what Jerome means to say.
Reply to Objection 6. Although the souls of the saints or of the damned are sometimes actually present where they appear, we are not to believe that this is always so: for sometimes these apparitions occur to persons whether asleep or awake by the activity of good or wicked angels in order to instruct or deceive the living. Thus sometimes even the living appear to others and tell them many things in their sleep; and yet it is clear that they are not present, as Augustine proves from many instances (De Cura pro Mort. xi, xii).
Source: Summa Theologica (New Advent)