I answer that, External things can be considered in two ways. First, as regards their nature, and this is not subject to the power of man, but only to the power of God Whose mere will all things obey. Secondly, as regards their use, and in this way, man has a natural dominion over external things, because, by his reason and will, he is able to use them for his own profit, as they were made on his account: for the imperfect is always for the sake of the perfect, as stated above (Q. 64, A. 1). It is by this argument that the Philosopher proves (Polit. i, 3) that the possession of external things is natural to man. Moreover, this natural dominion of man over other creatures, which is competent to man in respect of his reason wherein God's image resides, is shown forth in man's creation (Gen. 1:26) by the words: "Let us make man to our image and likeness: and let him have dominion over the fishes of the sea," etc.
Reply Obj. 1: God has sovereign dominion over all things: and He, according to His providence, directed certain things to the sustenance of man's body. For this reason man has a natural dominion over things, as regards the power to make use of them.
Reply Obj. 2: The rich man is reproved for deeming external things to belong to him principally, as though he had not received them from another, namely from God.
Reply Obj. 3: This argument considers the dominion over external things as regards their nature. Such a dominion belongs to God alone, as stated above. _______________________
SECOND ARTICLE [II-II, Q. 66, Art. 2]
Whether It Is Lawful for a Man to Possess a Thing As His Own?
Objection 1: It would seem unlawful for a man to possess a thing as his own. For whatever is contrary to the natural law is unlawful. Now according to the natural law all things are common property: and the possession of property is contrary to this community of goods. Therefore it is unlawful for any man to appropriate any external thing to himself.
Obj. 2: Further, Basil in expounding the words of the rich man quoted above (A. 1, Obj. 2), says: "The rich who deem as their own property the common goods they have seized upon, are like to those who by going beforehand to the play prevent others from coming, and appropriate to themselves what is intended for common use." Now it would be unlawful to prevent others from obtaining possession of common goods. Therefore it is unlawful to appropriate to oneself what belongs to the community.
Obj. 3: Further, Ambrose says [*Serm. lxiv, de temp.], and his words are quoted in the Decretals [*Dist. xlvii., Can. Sicut hi.]: "Let no man call his own that which is common property": and by "common" he means external things, as is clear from the context. Therefore it seems unlawful for a man to appropriate an external thing to himself.
On the contrary, Augustine says (De Haeres., haer. 40): "The 'Apostolici' are those who with extreme arrogance have given themselves that name, because they do not admit into their communion persons who are married or possess anything of their own, such as both monks and clerics who in considerable number are to be found in the Catholic Church." Now the reason why these people are heretics was because severing themselves from the Church, they think that those who enjoy the use of the above things, which they themselves lack, have no hope of salvation. Therefore it is erroneous to maintain that it is unlawful for a man to possess property.