43 Now this end and object, the common welfare in the temporal order, consists in that peace and security in which families and individual citizens have the free exercise of their rights, and at the same time enjoy the greatest spiritual and temporal prosperity possible in this life, by the mutual union and co-ordination of the work of all. The function therefore of the civil authority residing in the State is twofold, to protect and to foster, but by no means to absorb the family and the individual, or to substitute itself for them.
Source: Divini Illius Magistri (Vatican.va)