[Text found in Concilium, Rerum novarum: a hundred years of Catholic social teaching – edited by John Coleman and Gregory Baum.]
Seen from our present viewpoint, the encyclical’s teaching on ownership is very unsatisfactory. It roundly asserts, in opposition to the socialists, that possessing goods privately as personal property is a right given to human beings by nature. This right belongs to human beings since they are intelligent and rational, and therefore capable of foresight and providence with respect to the future. Hence they should be seen as having rights not only to consumer goods, but also to those which usage does not consume, and specifically, to land. 
Leo XIII, though without acknowledging it, seems here to be inspired by St Thomas Aquinas (2-2, q.66,a.i). But he is making a seriously erroneous interpretation. Thomas Aquinas does indeed devote the whole question 66 of his 2-2 to a thematic treatment of human dominion over things and the right to property. But he proceeds by parts. In a. I he merely asks if it is natural for human beings to possess external things; he replies in the affirmative through the argument of the reasonableness of human nature. But he is not yet speaking of private property, since he poses this question in a.2, where he asks if human beings can legitimately possess anything as their own. According to Aquinas, the dominion that is ‘natural’ to human beings as rational beings is a basic dominion which could be realized in social forms; this would guarantee their personal participation in the use and reasonable disposition of goods.
Speaking now in a.2 of ‘private property’, and feeling the weight of a Christian tradition that is clearly reticent about this and leans rather to the holding of goods in common,  St Thomas replies with a distinction: with respect to the use of external things, men should hold these as though they were in common, placing them at the disposition of others. Concerning the power to provide or dispose of these goods, on the other hand, the regime of private property is licit and even necessary up to a point. This does not stem from reasons of metaphysical anthropology, however, nor even from ethical ones, but from pragmatic considerations of greater benefit and more peaceful co-existence. 
To return to Rerum Novarum: there is a certain contradiction between affirming that human beings as rational beings have a right to private property, including land, and accepting that the majority of humankind possess nothing more to live on than the wages earned by their labour. 
To prove that the right to private property is natural. Rerum Novarum argues that by working on a part of nature, human beings award this to themselves as private property, since their work leaves a sort of stamp on it.  Here Leo XIII’s concept of private property coincides with John Locke’s, but without an important reservation added by Locke: at least when there is enough of this commodity for others to have use of it. All this betrays a vision of human existence à la Robinson Crusoe, which does not correspond to the complexity of social and historical reality, or take account of the cultural and technical dimensions of labour and consumption in modern society.
Rerum Novarum‘s two most important contributions to the question of ownership and labour are its affirmation that justice requires that wages should be sufficient for the upkeep of a ‘frugal and sober’ worker,’  and its proclamation of the right of workers to free association, including the autonomy of such associations.  Of wages, the encyclical notes that these are personal, but also necessary. Therefore, if a worker, forced by necessity, accepts inhuman conditions laid down by the employer or business, this is putting up with a violent injustice. Here Leo XIII is saying that the free market needs to be corrected by imperatives of justice. This is a viewpoint heavy with consequences.
2. Quadragesimo Anno
Forty years alter Rerum Novarum, Pius XI repeated its teaching on private property in Quadragesimo Anno. Here, however, its ‘social function’ is stressed.  The solution proposed to make this effective is perhaps its teaching on the ‘corporate order’.  But this proposal, made in a purely abstract way, turned out to be dangerously close to the syndicalist structure of totalitarian regimes (Italy, Portugal, Spain, Germany), which, while denying freedom of party and association, in fact submitted to capitalist interests. This is why later Popes, and the Second Vatican Council, without explicitly renouncing this aspect of Quadragesimo Anno have left it aside. In any case, Pius XI had insisted on the right to free and autonomous associations. 
Concerning the just wage, Pius XI added a clarification to Rerum Novarum‘s concept of a life-supporting wage: this should be sufficient reward to cover the human needs of the worker ‘and his family’. 
3. Addresses by Pius XII
Pius XII, in his radio address of 1 June 1941, makes an interesting observation: ‘Every man, as a living being endowed with reason, has in effect by nature the basic right to use the material goods of the earth, even when the detailed regulation of the practical application of this right is left to human will and the juridical authorities of nations.’’  Here the social teaching of the church is once more connected to the great patristic and mediaeval tradition. Private property and the free reciprocal interchange of goods are subordinate to ‘the natural end of material goods, and cannot be made independent of the primary and basic right, which concedes their use to all, but should rather serve to establish this right in conformity with this end.’ 
Pius XII’s teaching on private property is nevertheless laden with unresolved tensions, which emerge clearly from the radio address of 1 September 1944, the homily of 3 June 1950, and his 1952 and 1955 Christmas messages.  These texts clearly show an inadequate historical and social analysis and an excessive nostalgia for the world of peasants and guilds, seen as almost the only vehicles for safeguarding personal values. Such an outlook is of very little help in tackling the complex socioeconomic problems of the modern world realistically.
With regard to labour, Pius XII reaffirmed the full right of workers to free trade unions  and the right to make one’s labour the means of providing for one’s own life and that of one’s children.’ 
4. Mater et Magistra and Pacem in Terris
John XXII’s Mater et Magistra represents an advance on Pius XII’s teaching on the subject of property. This advance consists in the historical and sociological analysis of modern industrial society and the roles played in it by social security systems, professional expertise and rights founded on labour.  The ability of businesses to finance themselves sometimes produces a social debt, and workers should be granted a share by way of credit, especially if they are being paid no more than a subsistence wage.  Steps should be taken to change businesses into true human communities, giving workers an increasing share of co-responsibility in their administration and development. 
Besides these analyses of the complex make-up of society, Mater et Magistra continues to affirm the natural character of the right to private ownership, including that of the means of production, while allowing for a large measure of public ownership of these.  Two years later, in 1963, Pacem in Terris included in its list of human rights that to private property, ‘including the means of production’.  The Pope included this right among those held to be ‘universal, inviolable and inalienable’.  This natural right has to be interpreted in an equivalent and virtual sense: it means a personal participation in control of the means of production, not necessarily possessing them as private property.
5. Vatican II: Gaudium et Spes
Gaudium et Spes, promulgated on 7 December 1965, makes an important affirmation: ‘Human labour … is superior to the other elements of economic life. For the latter have only the nature of tools’ (67a). This virtually contains a radical critique of capitalism, which has seen and still sees the rights of capital as foremost. Gaudium et Spes reaffirms the universal destination of land and all it contains to the community, for the use of every human being and people: ‘Whatever the forms of ownership may be, as adapted to the .. legitimate institutions of people . . ., attention must always be paid to the universal purpose for which created goods are meant’ (69a). On private property, it is notably cautious, free from any ideological dogmatization of the right to ownership (71b). What it says of ownership should be applied not only to material goods, but also to intangible ones, such as professional skills (71c).
So a long road in the social teaching of the church comes to an end: it started with the abstract anti-socialism of Leo XIII and has ended with a certain openness to a variety of (non-dogmatic) forms and possibilities of democratic socialism, taking account of the great variety of historical, social, economic and cultural situations that exist.
6. Paul VI: Populorum Progressio
This, on the subject of private property, follows the same line of thinking as Gaudium et Spes. One interesting contribution is its condemnation of the ‘Manchester school’ of free-market capitalism (26). In its day, this passage aroused a considerable amount of anger among capitalists and a degree of contempt from many liberal economists. The Pope is not issuing a blanket condemnation of the desire for economic profit, necessary for a dynamic economy, which is essential today for the survival and development of humankind. What he condemns, on moral grounds, is private, individualistic profit taken as an absolute end in itself, to which everything else must be subordinated: the idea that maximizing return on capital is the supreme value. Against this form of capitalism, Populorum Progressio reminds us that the economy is at the service of people.
7. John Paul II: Laborem Exercens and Sollicitudo Rei Socialis
The encyclical Laborem Exercens of 1981 deals systematically with the subject of human work. Its central thesis is this: work is the correct standpoint from which to focus critically on the whole social question (3b). Work is a basic dimension of human existence (4a). But work needs to be humanizing, a process of human self-fulfillment (4-6, 9). The structures of out-and-out capitalism are incompatible with the human significance of work (14d). Work displays the essential solidarity and social nature of personal human existence (12d, 13b, 14d).
Some critics have condemned this as an excessive absolutization of the ‘metaphysics of work’, which they see as outdated, preferring the intersubjectivity of homo loquens to the man-nature dialectic of homo faber. But the social valuation of work includes or conjugates both dialectics. Laborem Exercens refers to the nineteenth-century workers’ movements for union and political rights in entirely positive terms (8b).
The encyclical Sollicitudo Rei Socialis of 1987 set out to bring the message of Paul VI’s Populorum Progressio up to date, stating the need for a forceful affirmation of the possibility of genuinely human development and authentic liberation (47a). It maintains a certain neutrality between capitalism and collectivism, ‘provided that the dignity of the human person is duly respected and promoted’ (41b). Both systems are so imperfect that they stand in need of radical correction (21a).
The Pope vigorously denounces the bureaucratic centralism of collectivist economies (15b). In the face of the problems which this brings, he reaffirms the individual’s right to economic initiative, going so far as to put this on a par with the right to religious freedom (15e, 42g). This seems excessive, particularly given the lack of analysis of what this ‘initiative’ might mean for every person in every situation within the complexity of the present economic systems and all their differing circumstances.
The encyclical proposes changes in the system of international trade, in the world monetary and financial system, and in the transfer of technology (43b-e). It argues for a greater degree of international control of all of these (43g). ‘Development,’ it argues,’ ‘should be carried out within the framework of solidarity and freedom, without ever sacrificing one to the other under whatever pretext’ (33h). John Paul II is not, however, envisaging the possibility of conflict between the two values, which leaves his statement somewhat up in the air. Vatican II’s Gaudium et Spes (75-d-e) is far more specific:
The proper relationship between socialization on the one hand and personal independence and development on the other can be variously interpreted according to the locales in question and the degree of progress achieved by a given people. When the exercise of rights is temporarily curtailed on behalf of the common good, it should be restored as quickly as possible after the emergency passes. In any case it harms humanity when government takes on totalitarian or dictatorial forms injurious to the rights of persons or social groups.
Translated by Paul Bums
 Cf. Leonis XII Acta XI, 1892, 100-2.
 Cf. J. M. Díez-Alegría, Cristianismo y propriedad privada, Bilbao 1988, 11—68
 Cf. 1-2, q.94, a.5 ad 3; 2-2, q. 57, a. 3,0; q. 66, a. 2,cff
 Cf. Acta XI, 129—31.
 Ibid., 102-3.
 Ibid., 129-31.
 Ibid., 133-5, 138-40.
 Cf. AAS 23, 1931, 191.
 Ibid., 204—6.
 Ibid., 205.
 Ibid., 200.
 Cf. AAS 33, 1941, 199.
 Loc. cit.
 Cf. AAS 36, 1944, 252-3; 42, 1950, 485-7; 45, 1953, 37; 48, 1956, 30.
 Cf. encyclical Sertum laetitiae, 1 September 1939, in AAS 31, 1939, 643.
 Radio address of 1 June 1941, in AAS 33, 1941, 201.
 Cf. AAS 53, 1961,426-7.
 Ibid., 420.
 Ibid., 423-4.
 Ibid., 427-31.
 Cf. AAS 55, 1963, 262.
 Ibid., 259.