Pope John XXIII
Mater et Magistra §152
Mater et Magistra: On Christianity and Social Progress
152 Private enterprise too must contribute to an economic and social balance in the different areas of the same political community. Indeed, in accordance with "the principle of subsidiary function," public authority must encourage and assist private enterprise, entrusting to it, wherever possible, the continuation of economic development.
Source: Mater et Magistra (Vatican.va)