Frank Luntz’s rebranding of the estate tax as the “death tax” was an impressive bit of marketing genius, but perhaps the greatest branding coup in modern American politics was the introduction of the term “intellectual property” into the policymaking lexicon. Intellectual property guarantees the owner exclusive rights to the use of an idea, but the uglier-sounding term “intellectual monopoly” is actually more accurate.

It may be too late to cast intellectual property out of our parlance in favor of intellectual monopoly, but it’s worth addressing the underlying philosophical claim to ideas as property. There is a strong consequentialist case for intellectual property in theory, but IP does not satisfy the Lockean definition of property and therefore shouldn’t grant the holder property rights under a natural-rights framework.

In their book The Captured Economy, Brink Lindsey and Steven Teles examine the claims of a natural right to intellectual property but stop short of either endorsing or denying such claims. Instead, they argue that, even if there is such a natural right, modern IP law violates it regularly (in particular, by preventing creators of “derivative works” under copyright law and independent co-inventors under patent law from making use of the products of their own minds). Here I’d like to go further and get to the merits of the matter.

To examine where property rights come from, let’s turn to John Locke’s Second Treatise of Government. To avoid a lengthy discussion about the merits of Locke’s arguments, let’s take the existence of property rights as he discusses them as a given: If I own myself and I put a part of myself, through my labor, into an unclaimed physical object, I should have exclusive claim to it in the same way I should have exclusive claim to my body and labor.

Why doesn’t this logic work for ideas? Most obviously and importantly, because physical property is scarce and rivalrous. If I take a piece of wood from the wilderness and whittle it into a spoon, anyone who uses that specific spoon is depriving me of my ability to use it.

This is at the nub of the problem Locke is trying to solve. Because physical objects are scarce and rivalrous in use, rights to use and control are necessarily exclusive: If one person gets to use and control the spoon, nobody else does. Locke is wondering how such exclusive rights got going if (as Locke believed) the physical world was given to people in common by their creator. He solves the riddle by asserting the right of self-ownership. Since our bodies and minds start out under our exclusive control, mixing our labor with external objects can bring them out of the common pool and into the realm of private property.

Ideas, on the other hand, are non-rivalrous, meaning their use by one party doesn’t prevent another from using them. If I come up with a new design for a wooden spoon and someone else uses the same idea (whether they learned it from me or developed it independently), my ability to use that design isn’t impeded.

What is impeded is my ability to monetize my design while denying others the ability to do the same. And in cases where the cost of innovation is high but the cost of imitation low, that impediment could end up mattering a great deal for society. Encouraging innovation by helping creators to monetize their creations is at the heart of the consequentialist case for IP. These considerations are, however, outside the scope of a Lockean case for intellectual property.

The problem Locke was trying to solve arises only because physical objects are rivalrous in use: To be useful, physical objects have to be used by somebody, but how can any one person assert control over objects if the whole physical world was given to us in common? This problem doesn’t exist for ideas; on the contrary, ideas are often most useful when they are widely shared.

Furthermore, while you have a right to the products of your mind just as you have a right to the products of your body, there’s an important distinction that must be made between an idea in your head and one that’s known to others. If I come up with an original idea for a widget, song, book, or joke, I could tweet it, tell it to a few close friends, or take it to the grave. This is a natural extension of someone’s right to their own mind.

But once an idea is out in the open, it’s analogous to someone selling or giving away physical property they appropriated from nature. As long as something is transferred voluntarily, the original owner can’t make a claim to this property once it changes hands (or in this case, minds). To maintain otherwise would violate the right to free exchange, a natural extension of the right to property.

Meanwhile, physical property could theoretically remain private forever, while even the staunchest supporters of IP rights believe ideas should enter the public domain at some point. Suppose Alice goes through the traditional process of Lockean appropriation to produce a spoon. That could be hers through the end of her life, but if she gives it to Bob it becomes his. He can then give it to Charlie, and so on. At no point in this chain does the spoon go back into the commons for someone else to appropriate. To believe that intellectual property is, in fact, property, one must also accept the possibility of this infinite chain of private ownership.

So not only does Lockean logic not hold for IP, but there’s actually a strong Lockean case to be made against intellectual property. Although Locke is remembered as a champion of private property rights, he was also deeply concerned with the limits of those rights. In particular, he worried about someone holding so much property that the holdings could not be used productively and others were unable to acquire similar property of their own.

Locke defines the upper limit on private property like this: “As much as any one can make use of to any advantage of life before it spoils, so much he may by his labour fix a property in: whatever is beyond this, is more than his share, and belongs to others.” My appropriation of a piece of wood may deny someone else the ability to use that specific piece of wood, but if “there is enough, and as good, left in common for others,” there is no problem. As long as there are enough trees to cut down, my spoon doesn’t prevent anyone else from making one.

Intellectual property, on the other hand, gives someone the exclusive right to the use of an idea anywhere, which would be an unacceptable restriction for Locke in the case of physical property. It would be akin to a monarch declaring that every tree in the land was his.

Let’s use another thought experiment to show the tension between traditional property rights and intellectual property rights. Suppose I, through voluntary exchange or Lockean appropriation, come into possession of all the raw material necessary to make a widget. These components are all mine, nobody else has any claim to them, and I came up with the design for the widget all on my own. But if I rearrange these components into a widget that is patented, the patent holder can sue me for violating their so-called property rights. Suddenly, the sum of my parts becomes someone else’s whole.

Finally, there’s a basic question about the right to the products of someone’s mind: what are the boundaries of those products? Few ideas are truly original. Those who create new ideas take their predecessors’ ideas and modify them or apply them in novel ways. If I share an idea that inspires somebody else to innovate, asserting property rights to my original idea has the effect of denying that person the ability to enjoy the fruits of their mental labor. After all, the underlying idea wasn’t theirs, but their application of it is.

None of the above should be taken as an argument that intellectual property is necessarily bad. There are serious and weighty consequentialist arguments for IP, but the social and private benefits from intellectual monopoly depend on how policy is designed, and reasonable people can disagree on what is the best design. Regardless, supporters of patent and copyright laws can’t rely on a natural right to property to justify their views.