Q113. What is the aim of the tenth commandment?

This commandment affirms and upholds the right to private property. The purpose of this commandment is the protection of the possessions that God has given to each person for the sustaining of life. If stealing is wrong, then it follows necessarily that every person must be able to hold on to what legitimately belongs to him. God therefore forbids in this commandment all forms of fraud, along with every clever scheme or method by which a neighbor's goods and possessions are damaged, reduced, or muddled in such a way that his rightful claim to them is lost or called into question. In forbidding these things, God at the same time requires all the virtues that work toward preserving our neighbor's goods and possessions. "You shall not steal" means: you shall not desire or attempt to take your neighbor's property through deception. You are therefore called to defend, preserve, and increase what belongs to him, and to give him what is rightfully his. God labels the forbidden actions theft so that He can gather under that single term, as the most obvious form of fraud, all other sins of a similar kind, including both what leads up to them and what follows from them.

The virtues of the eighth commandment.

Commutative justice is a virtue concerned with the acquisition of goods. It neither covets what belongs to others nor seeks to disturb the arithmetical equality that governs contracts and ordinary commercial dealings, including the purchase and exchange of goods under just laws. In essence, commutative justice means maintaining a proper balance between merit and reward, wages and labor, and so on, whether in acquiring or distributing goods. The Roman emperor Justinian, writing on the possession and division of property, identified several categories of ownership. Some things are common to all by natural right, such as air, water, the sea, and its shores. Some things are public, such as rivers, ports, and the use of riverbanks. Some things belong to no one, such as sacred, religious, and holy objects. The vast majority of things, however, are held by private individuals and are acquired in various ways. Anything transferred to a new owner, or taken by someone for themselves, either previously belonged to no one or to someone in particular. What belonged to no one becomes the property of whoever acquires it. What rightfully belongs to someone can only pass to another person in one of a few ways: by force and against the owner's will, by capture in war, or with the owner's consent, as through inheritance or contract. Property passes by inheritance either through a will or without one. A contract is an agreement between specific parties regarding the transfer, gift, or exchange of property under just and sound laws.