First let's define the terms. Socialism is the economical consequence, and a subset, of statism. Socialism is a form of statism which advocates collective or governmental ownership and administration of the means of production and distribution of goods.
Capitalism is based on the right to property.
Property is acquired thru trade, which is an exchange of values. Capitalism is the only system which does not deprive the individual of his rights. The right to life and its derivates, the rights to liberty, property, the pursuit of happiness, are all fulfilled in capitalism. People are free from the use of unearned force by the government, free to acquire and keep property, and to live in an ethical way. It is also the only system which allows progress thru the value of work.