His main argument was the lag between costs and prices.
Costs lag behind prices.
These, in my opinion, are key issues that are clearly set out by Fisher and that were later brought up and analyzed by Neoclassical economists during the Ph. As for the fact that many economists before the 20th century analized the relationship between monetary and real variables. It s a key topic in the history of economic thought. LIpsey may well have beaten Samuelson and Solow to the punch. This shows the Menu of Choice between Different Degrees of Unemployment and Price Stability, as Roughly Estimated from the Last Twenty-Five Years of American Data.