I noted in Monday’s blog – Modern Monetary Theory – what is new about it? – that I am working on a paper (with my colleague Martin Watts) that will form the basis of a a keynote talk I will give at the – International Post Keynesian Conference – which will be held at the University of Missouri – Kansas City between September 15-18, 2016. That talk will now be held at 15:30 on Saturday, September. 17, 2016. I also listed four areas where we would discuss the novel contribution that Modern Monetary Theory (MMT) has made to macroeconomics, despite the claims of both mainstream economists and some Post Keynesians that there is nothing new in MMT. The first two blogs on this topic covered the juxtaposition of employment versus unemployment buffer stocks and the implications of that for how we view the Phillips curve, a central framework in macroeconomics linking inflation to developments in the real sector (unemployment etc). Today’s blog considers another section of the paper – the dynamics of fiscal deficits and public debt. We consider the difference between deficit doves, who consider fiscal deficits are appropriate under some conditions but should be balanced over some definable economic cycle, which we argue has been the standard Post Keynesian position, and the MMT approach to deficits, which considers the desirable deficit outcome at any point in time to be a function of the state of non-government spending and the utilisation of the productive capacity of the economy. We argue that fiscal rules expressed in terms of some rigid balance to GDP target are not only meaningless but dangerous. Fiscal rules in MMT are only meaningful if related to the state of non-government spending and the utilisation of the productive capacity of the economy. This body of MMT work is clearly novel and improves on the extant Post Keynesian literature in the subject which was either silent or lame on these topics.