Murray Rothbard talked about how utilitarianism cannot get libertarianism right, but I think that is misguided: a proper understanding of utilitarianism in the broadest sense across a society (which is hard to achieve) is always equivalent to the natural law reading of things, because adherence to the natural law is what brings about prosperity in all cases when we define our rational actors with a sufficiently advanced understanding and long time horizon. Utilitarianism and positivism are thus extremely prone to error. It is an inefficient way of getting to the same answer that rational analysis provides, but it can yield interesting new details, particular states of affairs, and further hints for questions of rational inquiry, thus occasional empirical analysis is a welcome complement to the a priori rational method, in my view.