31 The rules, therefore, which Leo XIII issued in virtue of his authority, deserve the greatest praise in that they have been able to break down this hostility and dispel these suspicions; but they have even a higher claim to distinction in that they encouraged Christian workers to found mutual associations according to their various occupations, taught them how to do so, and resolutely confirmed in the path of duty a goodly number of those whom socialist organizations strongly attracted by claiming to be the sole defenders and champions of the lowly and oppressed.
Source: Quadragesimo Anno (Vatican.va)