I will define socialism to be a system of wealth distribution in which the wealthy willingly or forcibly give money to the poor. In the context of a governmental system we see socialism come about through high taxation of the wealthy, to give to the poor. I do not wish to debate the definition of socialism. I will however point out that "giving" to the poor is an intentionally vague term: giving of programs and giving of money should both be considered. In short, socialism is taking from the rich to give to the poor, without regard for the consent of the rich.
St. Thomas says that humans necessarily possess "things as their own".
"First because every man is more careful to procure what is for himself alone than that which is common to many or to all: since each one would shirk the labor and leave to another that which concerns the community, as happens where there is a great number of servants. Secondly, because human affairs are conducted in more orderly fashion if each man is charged with taking care of some particular thing himself, whereas there would be confusion if everyone had to look after any one thing indeterminately. Thirdly, because a more peaceful state is ensured to man if each one is contented with his own. Hence it is to be observed that quarrels arise more frequently where there is no division of the things possessed."
Further, Basil says about charity, "Why are you rich while another is poor, unless it be that you may have the merit of a good stewardship, and he the reward of patience?" There is no reason to believe that God could not impose socialism. Any musician will know that their livelihood is more or less out of their hands. This is true with every career. The hard working man is not rich solely because he is hard working, but because he has something to work hard on. So then why are some wealthy and others poor? God wishes to allow the wealthy to be charitable, and allow the poor to be patient.
Which is exactly why socialism is wrong, because it deprives the wealthy of the chance to freely exercise charity and the poor the chance to freely exercise patience. Remember that acts which are freely done are more virtuous than acts that are done due to outside pressure.Further more, it deprives the wealthy of the private property that they are rightly possess. Therefor socialism is a form of theft, because the government is taking what is not theres, and what is rightly owned by another.
Socialism can therefore not be defended on moral grounds or on social grounds because as St. Thomas pointed out, civil unrest is immanent when private property is denied.
There are many objections that could arise in the course of this that I omitted for brevities sake, so if you find it unconvincing in any way, please comment and I will respond. I didn't want to bog down the reader with a lengthy article, but the writings of St. Thomas (as always) and others provide convincing refutations of objections that could arise.
I plan on doing a further post on the purpose of government, and the purpose of taxation later. But as for now let it suffice that socialism is not the correct form of either.