Classical vs Modern Monetary Theory
I am intrigued that both Classical Monetary Theory (CMT) and Modern Monetary Theory (MMT) have a way of explaining how macroeconomics works, yet both think the other theory is wrong, while their own theory is right.
I think it is generally agreed that it is bad to let a sovereign currency inflate, i.e. devalue. It is tantamount to stealing from anyone who holds cash in that currency. It is embarrassing and to be avoided. But deflation is also to be avoided. It seems there is an international consensus that a currency should inflate, but only by a steady 2% per annum.
CMT believes that a thrifty, well run country should not run a deficit but should raise in taxation as much money as its government spends. If there is a deficit, CMT believes that printing money, or simply writing it into existence, causes inflation –– at least, in the absence of growth in the economy. For it believes that the value of a currency is a simple but inexorable function of the total quantity of 'Money' divided by the total quantity of 'Goods'. The preferred CMT response to a deficit is to borrow on the international bond market. But the CMT economists warn that too much borrowing will 'spook' the markets and interest rates will go up. The country will find itself stretched over a barrel as more and more of our tax goes straight off to pay interest on our National Debt. Should inflation occur, the Bank of England will raise interest rates, which inhibits the economy. It will curb spending by the indebted while cushioning (or even rewarding) the lenders.
MMT believes that deficits are vital if the economy is to grow, as it is the only way that money (currency) can enter the private sector. MMT holds that taxes are not required to "pay for government", for there is no reason why the money cannot be created (by a sovereign government; provided that it does not cause inflation). If there is idle capacity in the economy, printing money should stimulate the economy. If the economy is at full employment and surplus money is still chasing goods and services there will be inflation. The MMT answer to inflation is to raise taxes (rather than interest rates). This takes money off those that have it (rather than those that do not have it). Taxes can have other beneficial effects besides reducing demand for goods; it can reduce inequality, and it can reduce e.g. smoking or carbon dioxide emission.
Where CMT thinks that the value of a currency is set by the ratio of the total quantity of 'Money' (defined narrowly, or broadly?) to the total quantity of 'Goods', it could be argued that prices are set much more locally, by people who know neither the total quantity of 'Money', nor of 'Goods'; prices even respond to 'expectations'. Look at the way BP's profits soared when the Iranians closed the Strait of Hormuz. Perhaps the biggest difference between the two theories is in the different ways in which they propose to handle inflation. Though both schools aim to reduce the local availability of money, the CMT school would raise interest rates, inhibit business and penalise the indebted (CMT), while the MMT school would raise taxes.