As the title of this post indicates, we are back in the realms of calculus again. So I'm going to do something I couldn't really do on Twitter, namely define my terms, starting with what I mean by "inflation." At this point, any goldbugs reading this post can leave the room. Inflation on this occasion has nothing to do with the money supply.

We define inflation as the rate of increase of the price level. It is therefore the first derivative of the price level P with respect to time, t. We express this mathematically as dP/dt.

The fact that inflation is the first derivative of price with respect to time is, I think, the reason why economists get this wrong but others get it right. When answering the question, lots of economists took "accelerating" to refer to the price level rather than inflation. I shall return to this later on.