Libertarianism isn't the same thing as classical liberalism

The often-identified-as-libertarian scholar Richard Epstein makes that point in this post from 2014: My Rand Paul Problem.  As Epstein, one of today's intellectual leaders exploring free markets & smaller government, notes well, libertarianism often overlooks the complexity of modern life in favor of a simplistic & overly naive understanding of human behavior and society. Specifically, libertarianism's rejection of the legitimate authority of the State to enforce basic & fundamental norms overlooks the problem of what Epstein calls "holdouts" -- those who will not refrain from violence or other anti-social behavior:

The sad experience of history is that high transaction costs and nonstop opportunism wreck the widespread voluntary effort to create a grand social alliance to limit the use of force. Society needs a coercive mechanism strong enough to keep defectors in line, but fair enough to command the allegiance of individuals, who must share the costs of creating that larger and mutually beneficial social order. The social contract that Locke said brought individuals out of the state of nature was one such device. The want of individual consent was displaced by a consciously designed substantive program to protect both liberty and property in ways that left all members of society better off than they were in the state of nature. Only constrained coercion can overcome the holdout problems needed to implement any principle of nonaggression.

Epstein holes libertarianism below the water-line with that observation, grounded as it in in the prudential understanding of human nature that undergirds not only the classical liberal approach to politics but also the conservative approach as well.  Like its kissing cousin modern liberalism, libertarianism in practice denies the existence of sin or evil within human nature. And this denial has a host of concrete policy implications, as Epstein explains. The holdouts -- the anti-social and violent that will always be part of human society this side of heaven -- make a libertarian vision of society based purely on voluntary non-aggression impossible. Given human nature, such a society would invariably result in the strong preying on the weak, the sociopathic running riot among the decent. Indeed, it will not be society at all, but rather will be a state where human community will be dissolved to the point of, to use Thomas Hobbes' phrase, "a war of all against all."

As the Prophet Isaiah teaches, the wolf will indeed one day dwell with the lamb (Isaiah 11:6), but only when the fullness of God's reign is established. Until that happy day, human beings live in a fallen and sinful world, where the State is sometimes necessary to restrain the wicked and encourage virtue.