30 The injustice of certain situations cries out for God's attention. Lacking the bare necessities of life, whole nations are under the thumb of others; they cannot act on their own initiative; they cannot exercise personal responsibility; they cannot work toward a higher degree of cultural refinement or a greater participation in social and public life. They are sorely tempted to redress these insults to their human nature by violent means.
Source: Populorum Progressio (Vatican.va)