Pope Pius XI
Quadragesimo Anno §83
Quadragesimo Anno: On Reconstruction of the Social Order
83 Labor, as Our Predecessor explained well in his Encyclical, is not a mere commodity. On the contrary, the worker's human dignity in it must be recognized. It therefore cannot be bought and sold like a commodity. Nevertheless, as the situation now stands, hiring and offering for hire in the so-called labor market separate men into two divisions, as into battle lines, and the contest between these divisions turns the labor market itself almost into a battlefield where, face to face, the opposing lines struggle bitterly. Everyone understands that this grave evil which is plunging all human society to destruction must be remedied as soon as possible. But complete cure will not come until this opposition has been abolished and well-ordered members of the social body - Industries and Professions - are constituted in which men may have their place, not according to the position each has in the labor market but according to the respective social functions which each performs. For under nature's guidance it comes to pass that just as those who are joined together by nearness of habitation establish towns, so those who follow the same industry or profession - whether in the economic or other field - form guilds or associations, so that many are wont to consider these self-governing organizations, if not essential, at least natural to civil society.
Source: Quadragesimo Anno (Vatican.va)