10 You know, Venerable Brethren and Beloved Children, and understand full well the wonderful teaching which has made the Encyclical, On the Condition of Workers , illustrious forever. The Supreme Pastor in this Letter, grieving that so large a portion of mankind should "live undeservedly in miserable and wretched conditions," took it upon himself with great courage to defend "the cause of the workers whom the present age had handed over, each alone and defenseless, to the inhumanity of employers and the unbridled greed of competitors." He sought no help from either Liberalism or Socialism, for the one had proved that it was utterly unable to solve the social problem aright, and the other, proposing a remedy far worse than the evil itself, would have plunged human society into great dangers.
Source: Quadragesimo Anno (Vatican.va)