Is “thin libertarianism”–the view that libertarianism’s exclusive subject is political action–incoherent? Some writers think so:
If political philosophy is a branch of moral philosophy (and it is), then to have a political philosophy assumes having–even if only in an inchoate form–a moral philosophy.
If that’s true, then the claim (and it’s a rather common one) that libertarians should only concern themselves with permissible state action and take no stand on relationships and power structures outside of the state’s control is, I fear, rather incoherent. Because being a “thin libertarian”–as this view is called, in opposition to “thick libertarianism”–means (1) having a moral theory justifying your libertarianism but (2) believing that moral theory doesn’t also have something to say about relationships and behaviors outside of (the proper sphere of) politics.
Those moral beliefs then lead the libertarian to hold certain political beliefs about the legitimate role of the state–or, for some, beliefs about the state’s inherent illegitimacy. But if those moral beliefs are strong enough to motivate a political philosophy, they also must be strong enough to lead to conclusions about human interaction outside of the political sphere.
In other words, the simple fact that libertarianism is a moral philosophy as well as a political philosophy means that libertarianism is necessarily concerned with relations between private individuals and power structures not directly caused by political action.
I think there are two problems with this argument. The first is that the modifier “thin” limits the content of libertarianism, not the range of libertarian ideas. Rather than a kind of libertarianism that’s restricted to state action, “thin” libertarians claim that libertarianism’s content is limited to a prohibition on coercion. “Thin” libertarians have no objection to extending the range of a prohibition on coercion to private, non-state actors–a form of “thickness” that Charles Johnson calls “thickness in entailment.” “Thickness in entailment,” however, does not threaten the coherence of thin libertarianism because it does not concern the meaning of “thin” itself.
So my first disagreement is a semantic disagreement about the meaning of “thin.” But suppose we set that aside and consider the claim that “thin” libertarianism is incoherent because they believe their foundational moral theories have nothing to say about actions and institutions outside the of politics. This seems obviously mistaken to me because thin libertarians deny they hold their foundational moral views as libertarians. Their moral beliefs explain and justify their political beliefs, but not vice versa. One of the core features of “thin” libertarianism is the view that libertarianism is a political philosophy upon which many different moral theories can converge. Libertarianism, on this view, does not have a one-to-one relationship with a particular moral theory; that is, libertarianism does not explain anything about the rest of moral theory.
We can see this difference between libertarian political philosophy and moral theory by observing that empirical beliefs about the nature of politics and how states are likely to act also justify libertarianism, along with fundamental moral views. That is, libertarianism is jointly justified by moral beliefs about right action and by empirical beliefs about what politics is like. The relevance of these empirical beliefs to libertarianism demonstrates the distinctness of libertarianism from its underlying moral foundation.
What thin libertarians claim, then, is that “libertarianism” only refers to a set of moral beliefs and a set of empirical beliefs about politics. “Libertarianism” has nothing to say about power relations, gender roles, and other subjects thick libertarians want to talk about, simply in light of the meaning of “libertarianism.” That’s not incoherent–it’s a semantic argument.
So even if we accept that “thin” modifies the range rather than the content of “libertarianism,” there is nothing incoherent about a thin libertarianism that emphasizes the distinction between politics and the rest of moral theory. What we learn from this discussion, I think, is that the real disagreements between thin and thick libertarians are semantic disagreements about the meaning of “thin” and “libertarian.”