practically something else always does come in ahead, so far as his studies have gone.[185] My interest here is primarily in seeing the limitations Fisher imposes on his theory, and the qualifications he admits. If the business cycle is the typical transition period, during which his normal theory doesn't hold, when does the normal theory hold? When are the "normal periods"? There is no concrete period during which prices are neither rising nor falling, during which no important changes are taking place among the factors.[186] At times, Fisher seems to indicate that the normal period is imaginary (pp. 56, 159). Is, then, the contrast between a realistic "transition period" and a hypothetical "normal period" or are both hypothetical? Is the equation of exchange, too, a mere hypothesis? It should be, if it is to set forth a merely hypothetical theory. But no, Fisher insists on putting concrete data into it, and, indeed, gives an elaborate statistical "proof" of the equation. It, at least, is realistic. I confess that my certainty as to Fisher's meaning grows less, as I study his book with greater care. If the typical transition period be the business cycle, then the normal period could come only once, say, in ten years--or whatever period, regular, or irregular, one chooses to assign to the business cycle. The concrete price-levels for the greater part of the time are then surrendered to other causes. And the one-year cycle described in the equation of exchange is quite irrelevant. The equation of exchange should cover the whole business cycle, to fit in with the theory. Indeed, a realistic equation of exchange would then have no meaning at all, as the average price-level during the business cycle, played upon by a host of causes other than the factors described in the quantity theory, would not be the same as the average price-level which _would have_ obtained had only the "normal" causes been in operation.[187]