Since this thread is in general religious debates, I'll provide a reply grounded in theological considerations regarding "capitalism", rather than one that is purely poilitical-economic....
According to Catholic understanding of human society, the goods of the earth were, by natural law, originally ordained to be held in common as universal. God did not, from the beginning at least, institute division and privatization of property. There was no subjugation of one person to another envisioned under the primordial law of nature either. This all came about through later human artifice, chiefly on account of the fall from grace which led to original sin.
Thus, contrary to capitalist thought, private property is not "natural" as far as Catholic theology is concerned. However to avoid lawlessness, avarice and indeed violent anarchy in societies inhabited by sinful, imperfect men - private property is "necessary", so to speak and must be recognised by positive law. So despite the fact that the right to private property is not inherent in the nature of man, the state must protect it for the good of the social order.
However Catholic doctrine promotes a
limited ownership, whereas capitalism endorses an
absolute view of ownership.
In the absolute view of property ownership, it can only be relinquished at will
i.e. by charitable giving.
Because of the Catholic teaching on the universal destination of goods, we have a somewhat different take: in cases of need all things are common property.
St. Thomas Aquinas explained in the 13th century, following in the foot steps of the Church Fathers, that whatever resources the wealthy have in excess - beyond what is necessary for their comfort - belongs "
by right to the poor" such that it is not to be considered theft if the poor should use the property of the rich to satiate their hunger or need in extreme times. Had this been followed by Europeans in the 17th-early 20th centuries, I'm sure a lot of the problems underlying the French and Russian revolutions might have been mitigated, such that these catastrophes could have been avoided. Instead we had lords shooting to death starving poor men stealing the odd chicken to feed their impoverished families.
For while the Church believes that the right to property to be essential for the good of society and argues that it must be upheld, it does not see property ownership as an "
absolute" right like right-wing Libertarians would, for instance. It has a social dimension, namely the common good.
Not allowing the poor to share in our goods is to "steal" from their natural law right to a share in the common goods of the earth, since natural law takes precedence over any positive law, and therefore commit mortal sin:
http://www.newadvent.org/summa/3066.htm
In cases of need all things are common property, so that there would seem to be no sin in taking another's property, for need has made it common.
I answer that, Things which are of human right cannot derogate from natural right or Divine right. Now according to the natural order established by Divine Providence, inferior things are ordained for the purpose of succoring man's needs by their means. Wherefore the division and appropriation of things which are based on human law, do not preclude the fact that man's needs have to be remedied by means of these very things. Hence whatever certain people have in superabundance is due, by natural law, to the purpose of succoring the poor. For this reason Ambrose [Loc. cit., 2, Objection 3] says, and his words are embodied in the Decretals (Dist. xlvii, can. Sicut ii): "It is the hungry man's bread that you withhold, the naked man's cloak that you store away, the money that you bury in the earth is the price of the poor man's ransom and freedom."
Since, however, there are many who are in need, while it is impossible for all to be succored by means of the same thing, each one is entrusted with the stewardship of his own things, so that out of them he may come to the aid of those who are in need. Nevertheless, if the need be so manifest and urgent, that it is evident that the present need must be remedied by whatever means be at hand (for instance when a person is in some imminent danger, and there is no other possible remedy), then it is lawful for a man to succor his own need by means of another's property, by taking it either openly or secretly: nor is this properly speaking theft or robbery.
The 'Decretals' St. Thomas mentions are of course a reference to Gratian's compilation and codification of canon law, which included this precept in it.
This provides a moral basis for a degree of redistributive taxation in a country marked by grave disparities in wealth that are in turn caused by a free market guided by 'trickle-down' economics.
Thus we find Pope Leo XIII say in his 1891 social encyclical:
http://w2.vatican.va/content/leo-xii...m-novarum.html
37. Rights must be religiously respected wherever they exist, and it is the duty of the public authority to prevent and to punish injury, and to protect every one in the possession of his own. Still, when there is question of defending the rights of individuals, the poor and badly off have a claim to especial consideration. The richer class have many ways of shielding themselves, and stand less in need of help from the State; whereas the mass of the poor have no resources of their own to fall back upon, and must chiefly depend upon the assistance of the State. And it is for this reason that wage-earners, since they mostly belong in the mass of the needy, should be specially cared for and protected by the government.