I guess another way of making the point I'm trying to make is to complain that, when faced with a socialist who fears that unbridled capitalism leads to misery and poverty, the proper response to him is to argue that it does not. This, of course, is a job for economics, not philosophy.

Yet some libertarian philosophers seem to the socialist to be saying to him that the economic question is just moot, because all that counts is that no rights be violated and the consequences be damned.

Utilitarians rightly reject this draconian attitude, which they describe as fiat justitia ruat caelum, "Let Justice Be Done Though the Heavens Collapse," let justice be done though the world be destroyed.

This may look like Jeffery Friedman's objection to libertarianism, but it's actually a different one. My position is that economics is really where the action is: utilitarian arguments persuade, rights-talk doesn't.

The same goes for the socialist. He can talk about rights until he's blue in the face, but what everybody really cares about are the economic consequences.

Egalitarian social justice versus libertarian social justice is a crucial debate, yes. But, the value of doing justice derives, ultimately, from its indispensable utility. Justice is an instrumental good, not an absolute good. If doing justice really would destroy the world, then doing justice would not be good. It would be bad. If this were not so, then mercy could never be right.

I think the two cases are more reciprocal than they may sometimes appear. A conception of human welfare can only be meaningful if it includes intagibles - "ideals" or "values" (differing and even conflicting though they may be) like individual liberty. As John Stuart Mill points out in his essay 'Utilitarianism', utilitarianism is a means for discriminating betweens quantities of “happiness” (or welfare), not an assertion about the specific nature of the things that constitute it. He also conjectures, importantly, that no sane person would choose to forsake his or her higher capacities for an animal state of perfect material comfort.

In a final sense, then, I would say that utilitarianism (such as Mill defines it anyway) and, for want of a more specific term, “idealism” are inextricable – surely we are all utilitarians insofar as, all else being equal, we seek to maximise whatever values we have identified? Utilitarianism, as the comprehension of trade-offs and competition between our values, seems to me the necessary framework for applying any notion of natural rights to reality.

In the modern world, with advances in psychology, neuroscience, genetics, and other fields, there often seems to be a diminishing gap between the materials and what I have called the intangibles of human welfare. In itself, this progress is nothing but exhilarating, but there is also the disconcerting fact that, really since the Enlightenment, this momentum has fuelled the rationalistic conceit that has underpinned the imagination of the planned society. This is the idea that the “problem” of the human mind can now be “solved” along with the problems of the body – whether through the surgical removal of the imagination, as in Zamyatin’s ‘We’, or through the administering of Soma in ‘Brave New World’ (I have used fictional, and indeed critical, examples, but I think this attitude pervades political utopianism in much the same way). It is from this sort of conceit that I think the concept of utilitarianism must be constantly defended – hardly a new observation on my part, especially considering its presence in dystopian literature, but nonetheless an important one.

Ludwig von Mises, like Henry Hazlitt, Milton Friedman, and many other economists, argued for classical liberalism not on the basis of natural right, but on the basis of practical consequences for the maximization of human welfare. In other words, they argued a utilitarian case. Ayn Rand and others rest their case on a radically different foundation. Which case is stronger? (Spoiler: I take the utilitarian side.)