Pacem in Terris §98

⁹⁸ Since relationships between States must be regulated in accordance with the principles of truth and justice, States must further these relationships by taking positive steps to pool their material and spiritual resources. In many cases this can be achieved by all kinds of mutual collaboration; and this is already happening in our own day in the economic, social, political, educational, health and athletic spheres—and with beneficial results. We must bear in mind that of its very nature civil authority exists, not to confine men within the frontiers of their own nations, but primarily to protect the common good of the State, which certainly cannot be divorced from the common good of the entire human family