69 God intended the earth with everything contained in it for the use of all human beings and peoples. Thus, under the leadership of justice and in the company of charity, created goods should be in abundance for all in like manner. Whatever the forms of property may be, as adapted to the legitimate institutions of peoples, according to diverse and changeable circumstances, attention must always be paid to this universal destination of earthly goods. In using them, therefore, man should regard the external things that he legitimately possesses not only as his own but also as common in the sense that they should be able to benefit not only him but also others. On the other hand, the right of having a share of earthly goods sufficient for oneself and one's family belongs to everyone. The Fathers and Doctors of the Church held this opinion, teaching that men are obliged to come to the relief of the poor and to do so not merely out of their superfluous goods. If one is in extreme necessity, he has the right to procure for himself what he needs out of the riches of others. Since there are so many people prostrate with hunger in the world, this sacred council urges all, both individuals and governments, to remember the aphorism of the Fathers, "Feed the man dying of hunger, because if you have not fed him, you have killed him," and really to share and employ their earthly goods, according to the ability of each, especially by supporting individuals or peoples with the aid by which they may be able to help and develop themselves. In economically less advanced societies the common destination of earthly goods is partly satisfied by means of the customs and traditions proper to the community, by which the absolutely necessary things are furnished to each member. An effort must be made, however, to avoid regarding certain customs as altogether unchangeable, if they no longer answer the new needs of this age. On the other hand, imprudent action should not be taken against respectable customs which, provided they are suitably adapted to present-day circumstances, do not cease to be very useful. Similarly, in highly developed nations a body of social institutions dealing with protection and security can, for its own part, bring to reality the common destination of earthly goods. Family and social services, especially those that provide for culture and education, should be further promoted. When all these things are being organized, vigilance is necessary to present the citizens from being led into a certain inactivity vis-a-vis society or from rejecting the burden of taking up office or from refusing to serve.
Source: Gaudium et Spes (Vatican.va)