"Were it not for the fanatical refusal of some economists to admit that the price-level is in ultimate analysis effect and not cause, we should not be at so great pains to prove it beyond cavil." To explain this "fanatical refusal," Fisher alludes to the "fallacious idea" that the equation of exchange cannot determine the price-level, because the price-level has already been determined by other causes, usually alluded to as "supply and demand." He urges, however, that supply and demand, cost of production, etc., relate, not to the price-level, but only to particular prices: that the price-level is a factor prior to, and independent of, the particular prices, and is presupposed by theories like supply and demand, cost of production, etc.[338] The _reductio ad absurdum_, at first blush, looks impressive. One obvious criticism suggests itself, however, and it will be found to give a clue to a much more fundamental criticism: is it reasonable to assume a doubling of _all_ prices? Above all, must the assumption involve the doubling of the price of gold bullion? Part of the argument to show that gold bullion would not be minted rests on that assumption. But, more fundamental, for such an all round doubling of prices, no _cause_ could be assigned. Of course the hypothesis of an increase in prices without any cause is absurd, and Fisher easily disposes of it. But suppose we assign some _concrete causes_, outside the equation of exchange, which might affect prices, and see how the thing works then!