If I had one magic power, it would be to force every libertarian who talks about how simple and obvious the non-aggression principle is to read this. And then, if they’re still standing, this. And this.
I say “force,” not because I think that these are bad books. Both Thomson and Kamm are dazzlingly smart and talented philosophers, and these books show them at the height of their philosophical skill. It’s just that, at some level, the whole project strikes me as somewhat akin to arguing about how many angels can fit on the head of a pin. Or, perhaps more precisely, like arguing that no matter how many angels happen to be on the head of some particular pin, we are not morally permitted to divert a trolley away from it and toward a pin upon which fewer angels are resting.
Seriously, though, it’s surprising to me how disengaged most libertarians seem to be from serious contemporary philosophical work on deontology. If you think that the distinction between inflicting harm and allowing harm to occur is seriously important, if you think that causing harm in self-defense is permissible while causing harm aggressively is not, if you are, in short, seriously committed to the idea of a rigorous deontological morality, then it really is incumbent upon you to look at these books to see where such a system leads you once you start to grapple with the hard problems in a thoroughgoing way.
And when you’ve done that, and you come running and screaming and begging for some good ol’ sensible Richard Epstein, I will be waiting for you.