Libertarians are known for their opposition to war. However, there is no distinctly libertarian theory of war. As Matt Zwolinski has suggested, libertarianism is not a unified doctrine but a cluster of ideas. They include:
A commitment to private property.
A commitment to negative liberty.
Skepticism of political power and authority.
Confidence in free markets.
A commitment to normative and methodological individualism.
A belief in the significance of spontaneous order.
As we can see, war is not on this list. However, the usual libertarian arguments against war stem from these commitments. Those arguments are:
I. War violates the prohibition to initiate force (or initiate the violation of rights).
Libertarians who make this argument are divided. Some, like the first Murray Rothbard and Bryan Caplan, are pacifists: all wars are prohibited, even defensive wars, because they kill innocent persons. Others, like Harry Browne and Ron Paul, think that only wars in defense of one’s state (individual self-defense, art 51, UN Charter) are permitted. Thus, a war defense of an ally (collective self-defense) or a war to save people from massacres (humanitarian intervention) are not. This is a form of libertarian nationalism.
II. War interferes with the pursuit of personal projects
Michael Walzer (no libertarian himself) makes this argument. He calls it the tyranny of war. War forces men and women to fight, flee, die, and suffer, when they would rather be doing something else. This argument is quite congenial with Loren Lomasky’s idea of persons as rational project pursuers. Such view does not entail pacifism.
III. War has multiple deleterious effects:
War fosters nationalism, a doctrine notoriously menacing to freedom.
War is at odds with the progress and prosperity that stems from unhampered movements of goods, capital, and labor that cements human progress.
War fosters collectivism and regimentation which is inconsistent with the individualism that libertarians endorse.
War inflates the power of rulers who declare that war emergency measures are necessary to counter external threats.
A
commitment to libertarian ideals is consistent with either contingent pacifism or
with the contrary belief that some wars are morally justified. What is inconsistent with libertarian
doctrine is the militarist mentality. Such
mentality infects a free society by substituting rigid, hierarchical relationships for voluntary, spontaneous exchanges. Central
to the libertarian dislike of war is the conviction that persons are
not to be sacrificed to the collective goals of the state, for the good
reason that, for libertarians. there are no collective goals of the
state. War can only be justified for the sake of individual life and
liberty.