Pope Pius XI
Quadragesimo Anno §82
Quadragesimo Anno: On Reconstruction of the Social Order
82 The social policy of the State, therefore, must devote itself to the re-establishment of the Industries and Professions. In actual fact, human society now, for the reason that it is founded on classes with divergent aims and hence opposed to one another and therefore inclined to enmity and strife, continues to be in a violent condition and is unstable and uncertain.
Source: Quadragesimo Anno (Vatican.va)