5 We therefore lavish praise upon each and every one of the strictly Catholic workingmen's associations existing in Germany. We wish them every success in all their endeavors on behalf of the laboring people, hoping they will enjoy a constant increase. However, in saying this We do not deny that Catholics, in their efforts to improve the workers' living conditions, more equitable distribution of wages, and other justified advantages, have a right, provided they exercise due caution, to collaborate with nonCatholics for the common good. For such a purpose, however, We would rather see Catholic and non-Catholic associations unite their forces through that new and timely institution known as the cartel .
Source: Singulari Quadam (Vatican.va)