P, spread to M', and finally reach M last of all, leading to a new normal equilibrium which is stable. I shall later show cases of this sort.[188] The abstract formulation of Fisher's contrast will not, I believe, give us an answer as to the extent to which he thinks his quantity theory realistic. I find myself particularly in genuine uncertainty as to the point mentioned above: would an actual equation of exchange for the whole business cycle, made up of the averages of M, M', V, V', P and T for the whole period, exhibit the "normal" relations among these factors? Or would this "normal" relation only emerge concretely at some moment of time in the course of the cycle when the abnormal causes affecting the price-level happened to offset one another? Or is it true that no actual figures which might be found, either for a moment of time, or as averages for any given period, will exhibit the relations required, and that only a hypothetical equation, based on the figures for M, M', V, V', P and T that _would have been realized_ had there been no "disturbing" causes, will show these "normal" relations? If, as Fisher at times indicates--as in his reference to Boyle's Law (p. 296)--he is stating only an abstract tendency, which may be neutralized by other tendencies in the situation, so far as concrete results are concerned, then it is this last doctrine which we must take, and the concrete equation of exchange has little if any relevance. If, moreover, this last interpretation be given, then the whole of Fisher's elaborate statistical "proof" is pointless. The only sort of statistical proof which would be relevant would be of a much subtler sort, not a mere filling out of the equation of exchange by means of annual figures, but an effort to disentangle and measure the _importance_ of his tendency, as compared with other tendencies. But we have the other tendencies merely mentioned in qualitative terms, and we never find any definite statement, of mathematical character, as to how important they are.