Quadragesimo Anno §84

⁸⁴ Because order, as St. Thomas well explains, is unity arising from the harmonious arrangement of many objects, a true, genuine social order demands that the various members of a society be united together by some strong bond. This unifying force is present not only in the producing of goods or the rendering of services - in which the employers and employees of an identical Industry or Profession collaborate jointly - but also in that common good, to achieve which all Industries and Professions together ought, each to the best of its ability, to cooperate amicably. And this unity will be the stronger and more effective, the more faithfully individuals and the Industries and Professions themselves strive to do their work and excel in it.