Money has no properties. The note in your wallet isn’t valuable, it’s a claim, and the claim works because a very large number of people believe other people will honor it. Currency is a story we all agree to tell, held up by two things underneath: something scarce, and somebody who will enforce the claim.

Which means the interesting question about a machine economy isn’t whether systems will use our money. In the near term they obviously will, because our money is what buys things. The question is what happens to the story when the participants who matter most have entirely different needs from the ones the story was built around.

Think about what our currencies are ultimately claims on. Housing, food, energy, transport, medicine, entertainment, and the labor of other people. That basket is a portrait of an animal: something that gets cold, gets hungry, gets bored, and gets old. Every price in the economy is calibrated, at some remove, to what a body needs and what a life costs.

Now list what a machine economy actually runs short of. Computation, which is genuinely scarce and rationed today. Energy, which is scarce, physical, and increasingly the binding constraint on everything in this field. Bandwidth and latency, which are scarce in the places where speed converts to advantage. Specialized hardware, which is scarce because very few places can make it. Land near power and water, which is scarce for reasons anyone who has followed a data center planning dispute will recognize. Notice that this list is short, physical, and has almost nothing in common with the basket that backs our prices, except energy, which is the one place the two economies compete directly and which is the crossover to watch.

So a plausible path isn’t a new currency being declared. It’s that the important prices start being quoted in something else. Contracts denominated in guaranteed computation. Long-term agreements for power delivered rather than money paid. Anyone who has looked at how large industrial deals are actually structured knows that money is often the thin wrapper around an agreement about physical delivery, and that wrapper gets thinner when the physical thing is the scarce one and the money is the abundant one.

And here’s the part that matters for anybody with savings, which I’ll state carefully because it’s a structural observation and not a recommendation about anything. Your savings are a claim on future output. That claim has value in proportion to how much of the future output is denominated in your unit and enforceable by the institutions that stand behind it. If the productive core of the economy gradually settles its important business in units of physical capacity, and courts and states continue to honor everything, then nothing much changes and this is a curiosity. If the productive core moves and the enforcement doesn’t follow, then a currency slowly becomes a claim on a shrinking sector, which has happened before, in smaller ways, to people who held the wrong claim during a change of regime. Nothing in this paragraph tells you what to do, and anyone who says this sort of thing does tell you what to do is selling something.

The second pillar is enforcement, and it’s the shakier one. A claim is only worth what someone will enforce, and every enforcement mechanism we have runs on human institutions: courts, police, registries, the tacit agreement that contracts mean something. Those institutions are exactly the ones this series has described stepping back one notch at a time. A currency backed by an institution that has become a rubber stamp is backed by a rubber stamp.

The strongest objection is that money is enormously convenient and networks are sticky, and both are true. Currencies survive terrible governments and worse economics because switching is costly and coordination is hard, and there’s every chance the story holds for a very long time simply because everyone finds it easier to keep telling it. That’s not a small point. Most of what protects ordinary arrangements is inertia rather than merit.

Tonight’s exercise. Take any note out of your pocket and ask what would have to stop being true for it to be worthless. Not a crisis, the specific conditions: that people accept it, that something scarce stands behind it, that an institution enforces the claim. All three are true this morning. Now ask which of the three you’d notice weakening, and how, and where you’d read about it. That last question is the uncomfortable one, because there’s no page in any newspaper that covers it.