What would happen next? Nothing. Individual citizens would have paid-up pension plans with real financial assets inside them. The vouchers (assuming that anyone bothered to print them, instead of using electronic registers) would sit inside a vault in Threadneedle Street until such time as hard cash arrived in the Exchequer. Then the vouchers would be redeemed, the Bank of England's corresponding liability to the Treasury would be liquidated, and the value created when each voucher was issued would be withdrawn from the economy. The ghosts would have dematerialised. Job done.

Now, a few awkward types might have objections. You might say, for example, that this is simply an exercise in make-believe, with the vouchers only having a value because the government has arbitrarily decided they should have that value, and everyone else decides to play along with them.

Yes—and what do you think money is?

You might argue that it is nonsense to claim my vouchers would not somehow get into the "real economy" and that the process is nothing more than a government printing money and unleashing inflation.

Not really. We could expect a rise in the price of financial assets and a boost to investment. A slump is a good time to have those. Our ghost-money would not be haunting the shopping malls. The process is self-correcting because the value of the vouchers is clawed back when they are redeemed.