The third reason why the kingdom of God is called a city is this: that a kingdom has a monarchical form, which seems opposed to liberty; and yet all the citizens of heaven are free, and our mother, the Jerusalem which is above, is free, as the Apostle Paul writes to the Galatians. And that blessed Apostle knew what he was saying, since he was once caught up into the third heaven and into paradise, and had searched out the customs and laws of that city (Gal. 4; 2 Cor. 12). Therefore, since a kingdom seems to include servitude and a city liberty, that kingdom may be called a city in which those who serve the King are free. Now among the blessed inhabitants of heaven there is not a single and simple liberty, but a manifold one. For first, all those citizens are free from the servitude of sin; because the first liberty, which existed in the earthly paradise, was to be able not to sin; whereas the second liberty, far greater, in the heavenly paradise is not to be able to sin, as St. Augustine teaches in his book On Rebuke and Grace (ch. 11).
The second liberty is from the servitude of death, and is like the former: for Adam was free in the earthly paradise, in that he was able not to die; the sons of Adam are free in the heavenly paradise, in that they cannot die. Nor should anyone wonder that we place liberty in this—in not being able to do something—since not being able to sin and not being able to die mark the excellence of freedom from the servitude of sin and from the servitude of mortality. For he who cannot sin is not only free from sin, but is also so far removed from that servitude that he is certain and secure that death will never draw near to him—a liberty which God alone possesses by nature, as the Apostle says: "Who only hath immortality" (1 Tim. 6). For although the Angels and souls endowed with reason are said to be immortal by nature, because they have no principle of corruption in their nature, yet God, who created them, can also destroy them. But the Angels and the blessed among men are certain and secure, as we have said, that they will neither sin nor die, and are therefore most free from the servitude of sin and of death—which is a glorious participation in that liberty.
The third liberty is from necessity, and that a manifold necessity. For in this life mortal men are obliged to eat, to drink, to sleep, to labor; they must now stand, now walk, now lie down. But the blessed in heaven are subject to no necessity, but are free from every necessity; and this is that liberty of the glory of the sons of God of which the Apostle speaks in the Epistle to the Romans (Rom. 8).
How great this liberty is, can be attested first by poor men, secondly by spiritual men, and thirdly by the rich and the friends of this world. How greatly poor men labor to provide food and drink, clothing and a bed, and other necessities for themselves and their families! And how immense would be the thanks they would feel and render to those who freed them from this servitude of necessity! Nor are there lacking those who allow themselves to be drawn into thefts and robberies, or other evil arts, in order to procure the necessary supports of life; for they say with that unjust steward of the Gospel: "To dig I am not able, to beg I am ashamed; I know what I will do" (Luke 16)—I will defraud my master; that is, by theft or rapine I will free myself from the servitude of necessity. But this is to fall into a far heavier servitude, namely the servitude of sin and of the devil, the foulest enemy of the human race. Holy men, who long for heavenly things, regard the servitude of caring for the body as a heavy burden, since it both requires many things and steals a great portion of time from far better things. Eusebius writes in the Ecclesiastical History, on the testimony of Philo, that the first Christians who lived at Alexandria in Egypt under Mark the Evangelist were accustomed to take such delight in heavenly meditations that they never ate except after sunset, so that they gave the whole day and a great part of the night to heavenly studies and left scarcely a small part of the night for refreshing the body; and that some were even accustomed to forget bodily food for three whole days, and some for six entire days (Eccles. Hist. 2, ch. 16). And John Cassian in his Conferences, and Theodoret in his Religious History, testify that this same thing was afterwards common among many holy hermits. To all these, therefore, the servitude of bodily necessity seemed most grievous, and with the Apostle they cried out: "Unhappy man that I am, who shall deliver me from the body of this death?" (Rom. 7). Moreover, to the citizens of this world, especially the rich, this servitude of necessity is not unwelcome; yet if they were wise, they too would judge it most grievous. Food and drink have savor for them, and sleep is sweet on a soft cushion; but if they exceed due measure, they fill their bodies with diseases, to repel which they are forced to take bitter potions and to endure no slight pains. Then, whether they wish it or not, they must either be at enmity with God and endure His most grievous wrath, or fight for temperance and sobriety against the concupiscence of the flesh—a warfare which is beyond all doubt most laborious and most perilous. From so great and so irksome a necessity, therefore, are poor and rich, the upright and the wicked alike delivered, when they are delivered from the servitude of this wretched and manifold necessity.
The fourth liberty is from the law and its precepts. For "the law is not made for the just, but for the unjust," as the Apostle teaches in the first Epistle to Timothy (1 Tim. 1). Now none are more just than the blessed, who are confirmed in justice and cannot become unjust. It is indeed true that for the just dwelling in this world the law is not imposed as something threatening and pressing, since they obey the law of their own accord and with a willing mind; yet it cannot be denied that a law is still laid upon them, directing and binding them to do what the law commands and to flee what the law forbids. But the just who enjoy the liberty of the glory of the sons of God need no law, since in the Word they behold all justice and, confirmed in perfect charity, cannot turn aside from the will of God. A great good is this liberty, which delivers from all solicitude and is altogether contrary to the captivity and servitude of those unhappy ones who, bound hand and foot, will be cast into the exterior darkness and into the furnace of fire (Matt. 22), so that they can neither endure nor escape those torments. And yet there is no man who is not bound to undergo one or the other of these two so contrary fates (Matt. 13). But most men are so blinded by the smoke of present honor, or by the dust of earthly goods, that they neither see nor consider these things, until sudden destruction comes upon them (1 Thess. 5) and punishment opens the eyes that sin had closed.