David Friedman writes:

My problem with BHL is that I have been unable to get its supporters to tell me what it is.

Does he really believe that, or is this just a way of being cute? I dunno.

Anyways, if you look at the Stanford Encyclopedia of Philosophy, you see that the term “left libertarian” standardly refers to someone who believes:

1. That we have strong rights of self-ownership, and
2. That the world as a whole, or at the least the economic value of the world’s resources, are commonly owned.

Left-libertarianism is, standardly, the most cartoon form of regular libertarianism, plus an implausible thesis about who owns the world’s resources by default.

As for bleeding heart libertarianism, BHL’s standardly accept the following two principles and hold that they are morally weighty:

1. Every person has strong prima facie rights to an extensive sphere of civil and economic liberties.
2. In order for it to be reasonable to demand that other reasonable people comply with coercive institutions, those people should have a sufficient stake in those institutions. Coercive institutions should tend sufficiently to benefit every reasonable person subject to them.

1 is a thesis about liberty. 2 is a thesis about social justice. Different BHLs will fill in 1 and 2 in different ways. (For instance, in the real world, won’t some people always slip through the cracks through sheer bad luck, regardless of what institutions we have? Surely that doesn’t mean there are no legitimate institutions of any kind, right?)  Different BHLs might have different views about what to do if 1 and 2 conflict. (For instance, how badly do markets have to function before this overrides some of our prima facie economic rights?) But that’s BHL in the abstract.

Some people obtusely claim that BHL is just a defense of statism. Well, it could be, but that depends upon certain empirical claims, claims about how institutions function. A BHL could advocate anarcho-capitalism, a minimal state, or a more-than-minimal state that still gives great room for economic freedom, such as Switzerland or even Denmark.