(c) that, in general, money and volume of credit (taken together), velocities, and trade, are independent magnitudes, each governed by separate laws, though Fisher concedes _some_ reaction of trade on velocities; (d) in particular, that volume of money and credit has no influence on trade, and that trade has no direct influence on volume of credit. All these doctrines are necessary if the contention that an increase of money will proportionately raise prices is to be maintained, or if it is to be maintained that a decrease in trade will proportionately raise prices. I have analyzed each of these contentions, and I find justification for none of them. Not yet, however, have we reached the least tenable aspect of the quantity theory. There remains the contention that prices are passive, that a change, _originating_ in prices, and involving a change in the average price, or the general price-level, cannot maintain itself--that P is a passive function of the other five magnitudes of the equation of exchange. To this central fortress of the quantity theory we shall devote the next chapter. CHAPTER XV THE QUANTITY THEORY: THE "PASSIVENESS OF PRICES" Is the price-level passive? Is it true that while change may occur from causes outside the equation of exchange in volume of money, volume of trade, and velocities of circulation, a change in the price-level from causes outside the equation is impossible? Must the average of prices be a passive function of M, the V's, M' and T? Such is the general contention of the quantity theory, and such, very explicitly, is Fisher's contention. The price-level is always effect, and never cause (with slight modifications of the doctrine for transition periods) in its relations to the other magnitudes in the equation of exchange.