To rehash: the only world that follows the non-aggression principle is the grab-what-you-can world. In this word “nobody initiates force directly against another person’s body, but subject to that constraint, people regularly grab any external resource they can get their hands on, regardless of who has made or been using the resource.” This world follows the non-aggression principle because it forbids people from acting upon the bodies of others without their consent. Introducing the institution of property into such a world violates the non-aggression principle because it permits people to act upon the bodies of others without their consent (walk across an imaginary line on the ground and someone acts upon your body, usually the state).
That property violates the non-aggression principle is so obviously true that it is amusing anyone ever contends otherwise. The institution of property is the most statist, violent, aggressive, anti-libertarian, big government program in history. Through laws of one sort or another, people are violently restricted from nearly every single piece of the world around them. They do not consent to these restrictions, which are imposed from without, unilaterally and at the barrel of a gun. In the process, every shred of negative liberty and self-ownership is destroyed.
The takeaway from this analysis would seem to be that if you believe in the non-aggression principle, you must support the grab-what-you-can world. And that is strictly true. It’s the only world where people are free to do whatever they want provided they don’t act upon the bodies of others without consent. It is the only world where people cannot have their bodies acted upon by others unless they act upon someone else’s body first (i.e. self-defense). All other worlds fall short of this.
Since no one advocates such a world, it would seem as if this takeaway practically retires the non-aggression principle from consideration in the realm of economic philosophy. In its place, people will have to ignore non-aggression entirely, and construct other arguments to justify their preferred set of institutions. Generally, those ideas will center around positive theories of entitlement, which are theories of how much of our scarce resources each person is owed.
But I don’t think the non-aggression principle is impossible to salvage in these discussions.
One way to think about non-aggression is that there is something suspect involved in acting upon others bodies to prevent them from moving about and doing what they want or need to do. There is something problematic about creating institutions that restrict people in this manner, institutions of property included.
But instead of concluding that we therefore can’t do such a thing and must implement the grab-what-you-can world, we can say that we should only impose such institutions if we do so in a way that essentially strikes a fair deal with those whose negative liberty we are destroying. This is, essentially, what Robert Nozick has in mind when he says that you can blow up people’s negative liberty so long as you do not worsen their welfare.
As I argued before, this non-worsening requirement, when infused with a proper understanding of opportunity costs, generates the conclusion that we should blow up negative liberty in the most distributively egalitarian way possible. It generates the conclusion that, in order to be justified in imposing a regime of violent aggression against people (e.g. institutions of property), we have to target our institutions towards making sure the worse off are as well off as they can possibly be. Any set of institutions that fall short of that trade off with institutions that don’t fall short of that, and therefore the non-worsening requirement for the use of aggression is unsatisfied.
I am not saying you need this argument, but I don’t think it’s a bad one. If you are going to subject people to restrictions with regards to resource access, it seems only fair that those set of restrictions ensure people are as well off as possible. If you are going to use aggression to prevent people from having access to those things they need to live and flourish, you should ensure they have as equitable share of the things as possible.
Short of that, you find yourself in spectacles where someone is hungry and destitute, not because there is not enough to go around, but because you are using aggression to prevent them from grabbing what they need. They are starving when, within twenty feet of them, there is more food than anyone will ever eat, which they do not grab because they know that you will attack them and put them in jail if they do so.
In short, it seems like a proper appreciation of the perils of aggression (which again is present in every world except the grab-what-you-can world) require that people constructing institutions of resource distribution heed the wisdom of John Locke:
God, the lord and father of all has given no one of his children such a property in his peculiar portion of the things of this world, but that he has given his needy brother a right to the surplusage of his goods, so that it cannot justly be denied him when his pressing wants call for it, and therefore, no man could ever have a just power over the life of another by right of property in land or possessions, since it would always be a sin in any man of estate to let his brother perish for want of affording him relief out of his plenty.
Except, Locke doesn’t take the logic far enough.