53 Far different is the nature of work that is hired out to others and expended on the property of others. To this indeed especially applies what Leo XIII says is "incontestible," namely, that "the wealth of nations originates from no other source than from the labor of workers." For is it not plain that the enormous volume of goods that makes up human wealth is produced by and issues from the hands of the workers that either toil unaided or have their efficiency marvelously increased by being equipped with tools or machines? Every one knows, too, that no nation has ever risen out of want and poverty to a better and nobler condition save by the enormous and combined toil of all the people, both those who manage work and those who carry out directions. But it is no less evident that, had not God the Creator of all things, in keeping with His goodness, first generously bestowed natural riches and resources - the wealth and forces of nature - such supreme efforts would have been idle and vain, indeed could never even have begun. For what else is work but to use or exercise the energies of mind and body on or through these very things? And in the application of natural resources to human use the law of nature, or rather God's will promulgated by it, demands that right order be observed. This order consists in this: that each thing have its proper owner. Hence it follows that unless a man is expending labor on his own property, the labor of one person and the property of another must be associated, for neither can produce anything without the other. Leo XIII certainly had this in mind when he wrote: "Neither capital can do without labor, nor labor without capital." Wherefore it is wholly false to ascribe to property alone or to labor alone whatever has been obtained through the combined effort of both, and it is wholly unjust for either, denying the efficacy of the other, to arrogate to itself whatever has been produced.
Source: Quadragesimo Anno (Vatican.va)