Notable quotations from the papal encyclicalPacem in Terris (Peace on Earth)Pope John XXIII, 1963
The natural rights with which We have been dealing are, however, inseparably connected, in the very person who is their subject, with just as many respective duties; and rights as well as duties find their source, their sustenance and their inviolability in the natural law which grants or enjoins them....
Once this is admitted, it also follows that in human society to one man's right there corresponds a duty in all other persons: the duty, namely, of acknowledging and respecting the right in question. For every fundamental human right draws its indestructible moral force from the natural law, which in granting it imposes a corresponding obligation. Those, therefore, who claim their own rights, yet altogether forget or neglect to carry out their respective duties, are people who build with one hand and destroy with the other. (#28-30)
It is not enough, for example, to acknowledge and respect every man's right to the means of subsistence if we do not strive to the best of our ability for a sufficient supply of what is necessary for his sustenance. (#31-32)