This is a post for philosophers; my apologies to readers who have different interests.
I want to suggest that, perhaps, libertarians can claim Kant as one of them. I don’t say that this is the true interpretation (whatever that means) of Kant’s political philosophy, but that it is a plausible interpretation.
In the Doctrine of Right, Kant addresses the problem of justified coercion. He writes that coercion is justified when it is a hindrance to a hindrance to freedom (Kant, The Metaphysics of Morals, McGregor ed., 1992, p. 237). That is why state coercion against a criminal is justified: he is using his freedom to hinder someone else’s freedom. The formula may also justify the use of state coercion, in the form of taxes, to support institutions that are necessary to protect freedom –courts, police, armies. This interpretation, of course, sits well with libertarian doctrine. The state’s only job is to protect us against one another and against foreign enemies. But does the formula justify redistributive taxation?
Progressives think that Kant has the resources to justify coercive redistribution of wealth. To get there, they expand the notion of freedom to include positive freedom as well as negative freedom. Negative freedom is the absence of obstacles, barriers or constraints. Positive freedom is the possibility of acting — or the fact of acting — in such a way as to take control of one’s life and realize one’s fundamental purposes (I adopt these definitions from the Stanford Encyclopedia of Philosophy.) The progressive Kantian argument, then, is that once positive freedom is included in the formula, the state can hinder my freedom to exact resources that will help realize someone else’s positive freedom. Just as the state can tax me to fund institutions needed to protect negative freedom, so the state can tax me to subsidize folks whose positive freedom is impaired. (This is not the same argument as the one made by some modern Kantians, such as Ripstein and Weinrib, to justify the state’s duty to support the poor.)
Whatever the intrinsic merit of this view (and here I say nothing about this), it is hard to infer it from Kant’s formula. For Kant says that coercion is justified against someone who hinders someone else’s freedom, yet the person who is taxed for redistributive purposes is not hindering anyone’s freedom. The verb “hinders” denotes an action, not an omission. Just because someone is relatively well-off doesn’t mean she is hindering someone else’s positive freedom. In fact, the concept of hindering someone’s positive freedom makes no sense: if I am hindering someone from pursuing his goals, then it is already a case of negative freedom. Someone’s insufficient positive freedom is not caused by the person whose wallet the state is now raiding. (By the way, there are isolated passages elsewhere in Kant that suggest that he did not endorse state coercion to realize positive freedom, but they are inconclusive, especially because he does say some obscure things about the duty to aid the poor.)
I don’t want to be misunderstood. I don’t claim here that state redistribution is unjustified. I don’t even claim that a modified, jazzed-up version of Kantian principles (such as Korsgaard’s or Ripstein’s) would not justify redistribution. I only claim that those who seek support in Kant’s text should realize that, perhaps, progressive Kantianism had a pretty conspicuous dissenter: Kant himself.