It is no great deal for a libertarian to derive from the Non-Aggression Principle moral prohibitions against murder, rape, theft at gun-point, assault, and any number of other obvious violations of the NAP.
However, what about surreptitious theft? Let’s say somebody breaks into your home while you’re away, and steals some of your stuff. Is this really an aggression against you?
As I will explain momentarily, yes it is.
NON-AGGRESSION PRINCIPLE AND SELF-OWNERSHIP
Libertarian moral philosophy basically boils down to the Non-Aggression Principle and the idea of self-ownership.
Let’s do a quick recap. The Non-Aggression Principle states that you should not initiate the use of force against another human being. Such a principle obviously allows for defensive use of force.
Self-ownership is also simple: You own yourself. The alternative is of course that someone else owns you, i.e. slavery. So if self-ownership is accepted, then the first derivation we can immediately do is to say that you also own the product of your labor.
Why? Because whatever you have worked for or traded your work for represents an investment of time, and that time is an expenditure of your own life. If you own yourself, then you own the time you have on this world.
In this sense a man’s ownership of justly acquired property is really just an extension of his ownership of himself.
Now we can come back and answer the original question about surreptitious theft.
If you own yourself, and by derivation also own the product of your labor, then any taking of your property that you do not consent to is an indirect assault on you as a human being – on your time, and hence on a portion of your life.
Just as someone’s time can be taken by imprisonment, it can also be taken by theft.
If we really think about it, murder is the taking away of your future – of whatever time you have left. Imprisonment is the taking away of a part of that future, and an enslavement of your present. And theft is the taking away of a portion of your past – of whatever time you have spent acquiring the property that was then stolen from you.
I want to add only that the defining characteristic of theft is not the presence or threat of force, but the lack of consent in transfer of property. If consent is given, the transfer is called either a gift or a trade. If it is not, then it matters not whether the property was obtained through fraud, surreptitious theft, or the outright threat or use of force.