The magisterium has given ‘socialism’ a defined meaning and condemned it. No Catholic can adhere to Socialism in that sense and to adopt the term on the grounds that one adheres to a generically similar but formally distinct doctrine is to give very serious scandal.

“[T]he socialists … are striving to do away with private property, and contend that individual possessions should become the common property of all, to be administered by the State or by municipal bodies. They hold that by thus transferring property from private individuals to the community, the present mischievous state of things will be set to rights, inasmuch as each citizen will then get his fair share of whatever there is to enjoy.” Rerum Novarum 4

“Socialists, therefore, by endeavouring to transfer the possessions of individuals to the community at large, strike at the interests of every wage-earner, since they would deprive him of the liberty of disposing of his wages, and thereby of all hope and possibility of increasing his resources and of bettering his condition in life.” Rerum Novarum 5

“The socialists, therefore, in setting aside the parent and setting up a State supervision, act against natural justice, and destroy the structure of the home.” Rerum Novarum 14

“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.” Rerum Novarum 15

The Church teaches that the goods of the earth are given to the entire human race to provide for their subsistence and security and that by our application of fruitful labour to some part of the earth we appropriate that portion of the earth to provide for our own subsistence and security and that of our dependents. This right of property includes essentially the right to alienate these goods by sale, gift or bequest. Once provision is made for our own subsistence and security and that of our dependents whatever remains should be employed whether gratuitously or in exchange for labour or goods to assist others in providing for their subsistence and security. Only if this last obligation is not fulfilled does the right of property lapse and do third parties (destitute individuals and families or the civil power acting on their behalf but without respect of persons)  become entitled to treat the additional goods in question as if they had not been appropriated. Socialism essentially consists in the claim that the initial appropriation is undertaken by the community as a whole and so the right of property is vested in the community not in individuals or families and is only enjoyed by individuals and families by a concession of the community that may be modified or revoked.