Every piece of property I own down to my drawers was given to me voluntarily by another person through a mutually agreed on sale, or as a gift. On the other hand, every tax I pay is not voluntary. Income tax, social security, and other fees are removed from my pay by the government whether I want it to be or not. Sales tax is tacked on to something I buy without my consent. It's simply a question of consent versus coercion. A question of who owns what property can be adjudicated in a court of law. If you don't pay your taxes, some very unsympathethic people with guns and handcuffs will be paying you a visit.