15 And in addition to injustice, it is only too evident what an upset and disturbance there would be in all classes, and to how intolerable and hateful a slavery citizens would be subjected. The door would be thrown open to envy, to mutual invective, and to discord; the sources of wealth themselves would run dry, for no one would have any interest in exerting his talents or his industry; and that ideal equality about which they entertain pleasant dreams would be in reality the levelling down of all to a like condition of misery and degradation. Hence, it is clear that the main tenet of socialism, community of goods, must be utterly rejected, since it only injures those whom it would seem meant to benefit, is directly contrary to the natural rights of mankind, and would introduce confusion and disorder into the commonweal. The first and most fundamental principle, therefore, if one would undertake to alleviate the condition of the masses, must be the inviolability of private property. This being established, we proceed to show where the remedy sought for must be found.
Source: Rerum Novarum (Vatican.va)