Ad Petri Cathedram §39

³⁹ As Our predecessor, Pius XII wisely said, "In a nation that is worthy of the name, inequalities among the social classes present few or no obstacles to their union in common brotherhood. We refer, of course, to those inequalities which result not from human caprice but from the nature of things—inequalities having to do with intellectual and spiritual growth, with economic facts, with differences in individual circumstances, within, of course, the limits prescribed by justice and mutual charity." (13)