Ed Conway in the Times endorses Ken Rogoff's suggestion (pdf) that we should abolish cash. This seems to me completely infeasible, in at least three different ways:

- It is a grossly illiberal measure - the banning of capitalist acts between consenting adults, to use Robert Nozick's expression. I can't see voters tolerating this, especially as the move would be a means (pdf) of imposing a tax upon bank deposits: negative interest rates are analogous to a tax.

- Some 700,000 people don't have bank accounts. Many more use cash as a means of controlling how much they spend. For these, a cash ban would be a massive inconvenience.

- It wouldn't work. As John Cochrane says, people could get round the ban (and avoid the inconvenience of negative rates) by various measures such as buying gift cards or prepaying taxes and utility bills.

Despite all the talk of the growth of virtual currencies and digital payments, cash remains popular: notes and coins in circulation have been growing steadily for years, suggesting that the public has a use for them.

Banning cash, therefore, strikes me as one of the most impractical ideas I've heard - and seeing as I was a teenage Trot, that's a big claim.

Now, when intelligent men have silly ideas, ideology is often to blame. And it's not hard to see the ideology in this case. The main argument for banning cash (other than to inconvenience tax-dodgers, which is no stronger an argument now than it has been for years) is to facilitate sharply negative interest rates. But if you want to stimulate the economy - which might be a more pressing requirement come the next downturn rather than now - there's an obvious alternative: looser fiscal policy.

The only reason to suggest something as outlandish as banning cash is that you believe this alternative to be impossible.

Now, I don't believe this for a moment. In our world of negative real interest rates and a shortage of safe assets a bond-financed fiscal expansion is possible. And if it isn't, a money-financed one - a helicopter drop if you like - would be. Surely, either of these are more politically feasible than a ban on cash. To believe otherwise - given the difficulties of the latter - is, I suspect, to have an ideological animus against fiscal policy.

But let's say I'm wrong. Let's suppose that there are circumstances in which we are at the ZLB and in which fiscal policy is ruled out and in which we then face some sort of shock so bad as to require sharply negative interest rates and a ban on cash. (I leave the reader to judge how easy it is to imagine such a world.) Would such a world really vindicate the worldview of those who prefer monetary to fiscal expansion? Or would it instead be better evidence for the Marxian claim that capitalist economies are dangerously unstable?