"In recent times it has been held by many economists that the rate of current saving determined the supply of free capital, that the rate of current investment governed the demand for it, and that the rate of interest was, so to speak, the equilibrating price-factor determined by the point of intersection of the supply curve of savings and the demand curve of investment. But if aggregate saving is necessarily and in all circumstances exactly equal to aggregate investment, it is evident that this explanation collapses. We have to search elsewhere for the solution. I find it in the idea that it is the function of the rate of interest to preserve equilibrium, not between the demand and the supply of new capital goods, but between the demand and the supply of money, that is to say between the demand for liquidity and the means of satisfying this demand. I am here returning to the doctrine of the older, pre-nineteenth century economists. Montesquieu, for example, saw this truth with considerable clarity,— Montesquieu who was the real French equivalent of Adam Smith, the greatest of your economists, head and shoulders above the physiocrats in penetration, clear-headedness and good sense (which are the qualities an economist should have). But I must leave it to the text of this book to show how in detail all this works out."