No era will ever succeed in destroying the unity of the human family, for it consists of men who are all equal by virtue of their natural dignity. Hence there will always be an imperative need—born of man's very nature—to promote in sufficient measure the universal common good; the good, that is, of the whole human family.
In the past rulers of States seem to have been able to make sufficient provision for the universal common good through the normal diplomatic channels, or by top-level meetings and discussions, treaties and agreements; by using, that is, the ways and means suggested by the natural law, the law of nations, or international law.
In our own day, however, mutual relationships between States have undergone a far reaching change. On the one hand, the universal common good gives rise to problems of the utmost gravity, complexity and urgency—especially as regards the preservation of the security and peace of the whole world. On the other hand, the rulers of individual nations, being all on an equal footing, largely fail in their efforts to achieve this, however much they multiply their meetings and their endeavors to discover more fitting instruments of justice. And this is no reflection on their sincerity and enterprise. It is merely that their authority is not sufficiently influential.