I’ve been busy for the last week doing events for Economics in Two Lessons, so I didn’t have time to take part in the discussion arising from Harry’s post on alternatives to Sanders’ proposal to wipe out college debt.

In one way, that’s a pity because the key point of the book is the idea of opportunity cost – the true cost of anything, for us as individuals, and for society as a whole, is what you must give up to get it. More precisely, it’s the best alternative available to us.

Harry’s post was all about opportunity cost – what would be the best use of $1.6 trillion in public funds. However, the discussion was inevitably enmeshed in the complexities and inequities of US education, while comments making broader arguments about opportunity cost reasoning weren’t discussed in detail.

One of those broader arguments is the idea that, thanks to Modern Monetary Theory, there’s no need to worry about such questions. In the “chartalist” reasoning underlyng MMT, the fact that governments can issue their own sovereign currency means that there is no need to “finance” public spending by taxation; rather taxation is a tool used to manage aggregate demand so as to keep the economy fully employed but not at a point where excess demand creates inflation. That (essentially correct) position can easily slide into the (only subtly different, but radically mistaken) view that governments can spend money on anything they like with no need for any increases in taxes or cuts in other spending.

As I will argue over the fold, a correct version of MMT makes no such claim. Unfortunately, while avoiding the error themselves, a lot of MMT theorists have not shown much willingness to set their more naive followers straight.