Rand Paul brought some libertarian philosophy into the Republican presidential primary this week, in the form of the old "taxation is slavery" bumper sticker. He even indexed it to a handy percentage scale! Andrew Kaczynski has the tape: "I'm for paying some taxes. But if we tax you at 100 percent then you've got zero percent liberty. If we tax you at 50 percent you are half-slave, half-free."

Paul is probably getting his argument from Robert Nozick's Anarchy, State, and Utopia, which famously argued: "Taxation of earnings from labor is on a par with forced labor." (Note that not even he went so far as to say taxation was literally identical to slavery.) His book was probably the most convincing case that can be made for this stone-cold form of libertarianism, where all "redistributive" policy is morally abhorrent and only the night watchman state is permissible.

Nevertheless, it's still garbage. Nozick's book constructs a detailed procedural account of justice, arguing that redistributive taxation is theft because it is a coerced transfer. He was a smart guy, and it's very hard to get one's hooks into his argument. The weakness, as with all extremist accounts of property rights, is not with the logic but the premises — particularly when it comes to the very beginning of property.

Go back far enough in history, and there would have been no property of any kind. The moment somebody fences off a piece of land, it necessarily destroys the liberty of everyone else in the world, since they no longer have the right to access that land. Nozick admits this is the case, but still wants to set up initial property rights. So he embraces a concept that he calls the "Lockean proviso."

This proviso allows appropriation of unowned things, so long as it does not worsen the situation of anyone else. And what about people last in line, so to speak, who can't appropriate anything because everything is already taken? Well, they will benefit from the general prosperity brought on by market capitalism.

Note what kind of argument this is: It rests on the overall welfare-enhancing consequences of adopting Nozick's ideas.

The whole point of the "taxation is slavery-ish" argument is that infringing liberty to increase general welfare is morally impermissible. Yet here is Nozick, leaning on a boon to general welfare to justify a violation of liberty so he can get property rights going. This is no different from taxing the rich to provide food stamps, or from the kind of single-payer health insurance system that socialist Bernie Sanders endorses.

The upshot is that the austere libertarianism implied by Paul's statement is fundamentally unworkable. The horse stumbled right out of the gate, and has to be put down. Neither Milton Friedman nor Friedrich von Hayek went nearly so far. Even Nozick himself apparently abandoned it after a few years.

Let me also comment on Paul's gruesome tin ear on display here.

What is slavery really? In the U.S. context — and given the reference to Abraham Lincoln's "House Divided" speech, this is clearly what Paul was getting at — slavery was full property rights in human beings.

It was also incomprehensibly brutal. Owning a person presented a challenge to Southern capitalists, since slave labor has no monetary incentive to work. They solved this problem neatly, with daily violence. Set a steadily increasing daily work quota (pounds of cotton picked, typically), and if it was not achieved, make up the difference with an equal number of stripes with the whip.

In this way, Southern slaves were forced to increase their labor productivity by some 400 percent from 1800 to 1860, achieving a level that was not matched until the development of the mechanical cotton picker. Southern slavery thus robbed both the body and the mind, using systematic torture to force slaves into inventing and spreading techniques of extreme manual dexterity (picking cotton by hand is very difficult).

So if Rand Paul really believes that 1 percent taxation is exactly equal to 1 percent slavery, why doesn't he sound like an abolitionist? Why not seize one of the federal armories in an attempt to start an all-out war against a monstrous injustice? Indeed, by this measure there would be more slavery today (about 27 percent of GDP taxed) than in in 1860 (1.4 percent taxed, 12.6 percent of the population enslaved).

Only a moral idiot would think to make such an equivalence.