From Pope Benedict XVI’s encyclical Caritas in Veritate (2009):
In a climate of mutual trust, the market is the economic institution that permits encounter between persons, inasmuch as they are economic subjects who make use of contracts to regulate their relations as they exchange goods and services of equivalent value between them, in order to satisfy their needs and desires. The market is subject to the principles of so-called commutative justice, which regulates the relations of giving and receiving between parties to a transaction. But the social doctrine of the Church has unceasingly highlighted the importance of distributive justice and social justice for the market economy, not only because it belongs within a broader social and political context, but also because of the wider network of relations within which it operates. In fact, if the market is governed solely by the principle of the equivalence in value of exchanged goods, it cannot produce the social cohesion that it requires in order to function well. Without internal forms of solidarity and mutual trust, the market cannot completely fulfil its proper economic function. And today it is this trust which has ceased to exist, and the loss of trust is a grave loss. It was timely when Paul VI in Populorum Progressio insisted that the economic system itself would benefit from the wide-ranging practice of justice, inasmuch as the first to gain from the development of poor countries would be rich ones.90 According to the Pope, it was not just a matter of correcting dysfunctions through assistance. The poor are not to be considered a “burden,”91 but a resource, even from the purely economic point of view. It is nevertheless erroneous to hold that the market economy has an inbuilt need for a quota of poverty and underdevelopment in order to function at its best. It is in the interests of the market to promote emancipation, but in order to do so effectively, it cannot rely only on itself, because it is not able to produce by itself something that lies outside its competence. It must draw its moral energies from other subjects that are capable of generating them.
90 Cf. no. 49: Acta Apostolicæ Sedis [AAS] 59 (1967), 281.
91 John Paul II, Encyclical Letter Centesimus Annus, 28: AAS 83 (1991), 827-828.
— Caritas in Veritate 35