In the comments section of my post on Adam Smith and the Ayr Bank , frequent commenter John S. brought up the real bills doctrine . The phrase real bills doctrine gets thrown around a lot on the internet. To muddy the waters, there are several versions of the doctrine. In this post I hope to dehomogenize the various versions in order to add some clarity. 1. Lloyd Mints's version We may as well start with Lloyd Mints's version, since he coined the phrase real bills doctrine back in 1945 on his way to denouncing the doctrine. Mints taught at the University of Chicago and mentored Milton Friedman. [1] Here is Mints: The real-bills doctrine runs to the effect that restriction of bank earning assets to real bills of exchange will automatically limit, in the most desirable manner, the quantity of bank liabilities; it will cause them to vary in quantity in accordance with the "needs of business"; and it will mean that the bank's assets will be of such a nature that they...