In general, I conclude that the price-level, under the laws governing particular prices, supply and demand, cost of production, the capitalization theory, the imputation theory, etc., can vary of its own initiative, independently of prior changes in the quantity of money, or of volume of trade, or other factors that the quantity theory stresses; and that these changes in the price-level (or in the particular prices which govern the price-level) can maintain themselves, and compel a readjustment in trade, credit, money and velocities, to correspond. This conclusion strikes at the very heart of the quantity theory, and, if valid, leaves the quantity theory disproved. More fundamentally, I should put it, prices can change because of changes in the psychological values of goods. These values are _social_ values, and are to be explained only by a social psychology. But for the present it has seemed best to me, as a means of attracting sympathetic attention from a wider circle of economists, to make use of the less debated doctrines of the science in attacking the quantity theory. It is not necessary to rest the case on my own special theory of value. Supply and demand, cost of production, the capitalization theory, the imputation theory--the general laws of the concatenations and interrelations of prices--are quite adequate for the confutation of the quantity theory. They are laws concerned with particular prices, and the price-level is nothing but the average of particular prices. Whatever explains, really explains, the particular prices, also explains the price-level. Fisher, as we have seen, is not of this opinion. Although he has defined the price-level as an average of particular prices[349] he none the less exalts this average into a causal entity, prior to and master of the particular prices out of which it is derived, of which it is a mere average.[350] This average, he maintains, is presupposed in the determination of all particular prices.[351] This seems to me a wholly untenable position. _Ex nihilo nihil fit._ There cannot be _more_ in the average than there is in the particulars from which it is derived. In point of fact, there is necessarily vastly less. All the concrete causation is lost. The average, in itself, is nothing but a _statement_, a summary of _results_. I know nothing more metaphysical in the history of economic theory than this hypostasis of an average.[352]