43 We now approach a subject of great importance, and one in respect of which, if extremes are to be avoided, right notions are absolutely necessary. Wages, as we are told, are regulated by free consent, and therefore the employer, when he pays what was agreed upon, has done his part and seemingly is not called upon to do anything beyond. The only way, it is said, in which injustice might occur would be if the master refused to pay the whole of the wages, or if the workman should not complete the work undertaken; in such cases the public authority should intervene, to see that each obtains his due, but not under any other circumstances.
Source: Rerum Novarum (Vatican.va)