Lots of people have already responded to this (I didn’t reblog the whole reply chain, to save space), but here’s how I think of this.
“Property rights” are like logical validity, not logical soundness. They don’t state that a given property distribution is just. They’re a set of rules that you can follow to transform one property distribution into another property distribution. The best you can do is say “Given the property distribution yesterday, all the changes that happened between then and now have preserved property rights.”
(I know this wasn’t Locke’s view, but I think Locke’s view was kind of hack-ish)
According to the people who want property rights, these rules maximize economic productivity (not just in the boring sense where GDP is 1% higher, but at the extremes also in the sense where you are living in houses instead of starving in the mud). Starting with whatever original distribution of property, the economy will produce the most if the distribution only changes in ways that follow the rules of property rights.
So for example one part of property rights could be described as “don’t steal”. This isn’t a claim about the justice of a certain distribution of property. It’s just a claim that whatever your distribution of property today, if you want to maximze economic productivity, the changes you make to that distribution in order to get the distribution of property tomorrow, shouldn’t involve stealing. And the “justification” is that if there’s stealing, then people won’t produce as much, because they expect the stuff they produce will just get stolen before they can enjoy it.
(There are some ways that the usual conception of property rights departs from what seems to maximize economic productivity. For example, the economy would be more productive if we stole all the money from useless rent-seekers and spent it on infrastructure. I think the idea of a Schelling fence ( https://www.lesswrong.com/posts/Kbm6QnJv9dgWsPHQP/schelling-fences-on-slippery-slopes ) explains why we don’t do that - you could also analogize this to rule utilitarianism vs. act utilitarianism, or to why the rule for maximizing information flow is “freedom of speech” and not “freedom of speech except for dumb people who say dumb things and so aren’t contributing to useful information flow”.)
“But doesn’t this mean you could redistribute all property fairly, just once, and then stick to property rights from there so that the economy could still do well? Especially if you did this as a surprise, so that nobody saw it coming and produced less?”
I don’t think this would be the *worst* idea (though obviously there are practical considerations). But I also think it wouldn’t help much. There’s decent evidence that the effects of initial property allocation “decay” across generations. The most famous example is that the state of Georgia randomly distributed stolen Cherokee lands by a lottery. The settlers who won the lottery got free land worth about $70,000 in today’s money, the settlers who lost got nothing. Their descendants were equally wealthy after about two generations. Most descendants of the robber barons of the Gilded Age are still well-off but not robber barons themselves, etc. On the other hand, every generation some new people become rich through upward mobility - the most obvious example in the US being immigrants who all came to the country with nothing but some of them quickly got richer or poorer than others. So even if we distributed everything equally in generation 1, pretty quickly some people would quickly get more or less because of connections, skills, or luck. By generation 2 or 3, your only solace would be that your money depended on who your father or grandfather was, as opposed to your great-great-great-grandfather. After a few generations, you would have to redistribute everything again. But at this point you can’t credibly say the redistributions are happening “just once”, and you will get all the normal effects of people expecting to have their property taken from them and so producing less.
(slightly related: Coase’s theorem says that under certain conditions, property rights will still produce the economically efficient outcome regardless of the initial allocation of property. Those conditions don’t all hold but the theorem seems to be pretty close to reality. So from an economic efficiency standpoint, you might as well start with a random property allocation and let things develop naturally from there. So either the current property distribution, or a hypothetical fair property redistribution, could maximize economic efficiency if you followed property rights thereafter.)
This is why I support something more like a universal basic income. Instead of seizing all property and redistributing it once every few generations, you seize a small percent of property and redistribute it each year. It’s fairer (since it doesn’t disproportionately harm/benefit people at one specific time), and more efficient (since it only takes away a small percent of property, most of the incentives of private property still work and encourage people to produce, plus you can use the efficient tax literature to figure out how to disrupt incentives as little as possible, eg Georgism). As far as I can tell, this is the best way to balance the considerations in favor of property rights with the considerations of redressing the unfairness of some people starting with more than others.