Bryan runs familiar hard libertarian counterexamples to BHL concerns
about the least well-off largely by testing our claims about social
justice against micro-level examples, such as an island with ten people,
many of whom wish to redistribute the fruit of "Able Abel's" labor.
Many replies suggest themselves, but let me offer one.
A conception of social justice helps to specify what counts
as the fruits of one's labor in a massive system of social cooperation
which depends on a vast range of conventional rules. That's why Bryan's
testing social justice against micro examples is problematic, because it
masks indeterminacy in macro-level social norms that we want a
standard of social justice to evaluate. Consider the many "incidents"
of property rights, such as whether homesteading land means that you own
the air miles above your plot. In Bryan's case, disputes over the
"height" of our property don't matter. But in our complex society, such
disputes matter a lot because the efficiency of airline travel depends
on how they are resolved. A conception of social justice can help us
determinate what system of efficient property rights can be morally
justified in this case of indeterminacy.
One small point: There's plenty of "indeterminacy" even on a desert island with ten people. For starters: Able Abel, like all humans, breathes on others without their consent. A stickler might accordingly charge him with battery or trespass. Question: Is this indeterminacy a good argument for treating him like a slave?