Rodzilla!:When I used to get hung up on this same question, I changed tack slightly by trying to validate the opposite of property rights. When I tried to prove to myself that property rights were invalid, I quickly discovered that the notion was self-contradictory to the point of absurdity...
Except it's ownership of your hands (to take Stefan's example) that is the absurd self-contradiction. You can't sell your hands; therefore you don't own them.
You can't define self-contradictions into existence. You can't define "non-transferable ownership" into existence.
If you could do that, then you could define God into existence. This isn't even philosophy 101, it's philosophy 001.
It is mind-boggling to see reasonably smart people give precise justifications for blatant stupidity.