5 But it is not the present sanguinary strife alone that distresses the nations and fills Us with anxiety and care. There is another evil raging in the very inmost heart of human society, a source of dread to all who really think, inasmuch as it has already brought, and will bring, many misfortunes upon nations, and may rightly be considered to be the root cause of the present awful war. For ever since the precepts and practices of Christian wisdom ceased to be observed in the ruling of states, it followed that, as they contained the peace and stability of institutions, the very foundations of states necessarily began to be shaken. Such, moreover, has been the change in the ideas and the morals of men, that unless God comes soon to our help, the end of civilization would seem to be at hand. Thus we see the absence from the relation of men of mutual love with their fellow men; the authority of rulers is held in contempt; injustice reigns in relations between the classes of society; the striving for transient and perishable things is so keen, that men have lost sight of the other and more worthy goods they have to obtain. It is under these four headings that may be grouped, We consider, the causes of the serious unrest pervading the whole of human society. All then must combine to get rid of them by again bringing Christian principles into honour, if We have any real desire for the peace and harmony of human society.
Source: Ad Beatissimi Apostolorum (Vatican.va)