analysis and involved chains of reasoning, which seldom carry real conviction The denial to economics of the dramatic and direct evidence of the"crucial"experiment does hinder the adequate testing of hypotheses; but this is much less significant than the difficulty it places in the way of achieving a reasonably prompt and wide consensus on the conclusions justified by the available evidence. It renders the weeding-out of unsuccessful hypotheses slow and difficult. They are seldom downed for good and are always cropping up again There is, of course, considerable variation in these respects Occasionally, experience casts up evidence that is about as direct dramatic, and convincing as any that could be provided by controlled experiments. Perhaps the most obviously important example is the evidence from inflation on the hypothesis that a substantial increase in the quantity of money within a relatively short period is accompanied by a substantial increase in prices Here the evidence is dramatic, and the chain of reasoning required to interpret it is relatively short. Yet, despite numerous instances of substantial rises in prices, their essentially one-to one correspondence with substantial rises in the stock of money, and, the wide variation in other circumstances that might appear to be relevant, each new experience of inflation brings forth vigorous contentions, and not only by the lay public, that the rise in the stock of money is either an incidental effect of a rise in prices produced by other factors or a purely fortuitous and unnecessary concomitant of the price rise One effect of the difficulty of testing substantive economic hypotheses has been to foster a retreat into purely formal or ie an extremely important place in economics and other sciences as a specialized language or "analytical filing system. Beyond this formal logic and mathematics, which are both tautologies. are essential aids in checking the correctness of reasoning, discovering the implications of hypotheses, and determining whether supposedly different hypotheses may not really be equivalent or wherein the differences lie But economic theory must be more than a structure of tautologies 9. See"Lange on Price Flexibility and Employment, "infra, passim11 analysis and involved chains of reasoning, which seldom carry real conviction. The denial to economics of the dramatic and direct evidence of the "crucial" experiment does hinder the adequate testing of hypotheses; but this is much less significant than the difficulty it places in the way of achieving a reasonably prompt and wide consensus on the conclusions justified by the available evidence. It renders the weeding-out of unsuccessful hypotheses slow and difficult. They are seldom downed for good and are always cropping up again. There is, of course, considerable variation in these respects. Occasionally, experience casts up evidence that is about as direct, dramatic, and convincing as any that could be provided by controlled experiments. Perhaps the most obviously important example is the evidence from inflation on the hypothesis that a substantial increase in the quantity of money within a relatively short period is accompanied by a substantial increase in prices. Here the evidence is dramatic, and the chain of reasoning required to interpret it is relatively short. Yet, despite numerous instances of substantial rises in prices, their essentially one-to one correspondence with substantial rises in the stock of money, and, the wide variation in other circumstances that might appear to be relevant, each new experience of inflation brings forth vigorous contentions, and not only by the lay public, that the rise in the stock of money is either an incidental effect of a rise in prices produced by other factors or a purely fortuitous and unnecessary concomitant of the price rise. One effect of the difficulty of testing substantive economic hypotheses has been to foster a retreat into purely formal or tautological analysis.9 As already, noted, tautologies have an extremely important place in economics and other sciences as a specialized language or "analytical filing system." Beyond this, formal logic and mathematics, which are both tautologies, are essential aids in checking the correctness of reasoning, discovering the implications of hypotheses, and determining whether supposedly different hypotheses may not really be equivalent or wherein the differences lie.. But economic theory must be more than a structure of tautologies 9. See "Lange on Price Flexibility and Employment," infra, passim