¹ This is to convey an idea of a “concept.” It is not required that available statistics permit actual evaluation of a figure. For periods in which adequate statistics are not available the definition simply reads: if available indications justify the belief that the trend values …

² Good examples are afforded by the third book of the Wealth of Nations and by Chapters 2 and 3 of the first book of Marshall's Principles. These examples are “good” in the sense that they represent well what economists have had and have to say on the subject in general—but not otherwise. I fancy that historians will read both with a smile, good-natured or not.

³ Such incidental comments on what caused positive or negative growth in individual cases, for example, in the history of an individual industry, are all the more valuable when they are preferred unintentionally, that is, if their bearings upon a general theory of growth is not perceived by the writer. For in this case the writer's opinion is not vitiated by his philosophies or preconceptions.

⁴ This does not necessarily imply emphasis upon “race.” For it is possible to hold that the range of variation in “ability” (for definiteness, think of the Spearman factor) among individuals is very great and even that “ability runs in stocks” (K. Pearson) without attaching importance to the racial aspects of these stocks (that is to say, without believing that this ability of human stocks is differentiated racially). It is, however, interesting to note that prominent economists, especially English ones, have been in the habit of emphasizing race. Nobody thinks of J. S. Mill—the utilitarian radical!—and A. Marshall as “racialist.” Yet the racial note is unmistakable in the general introductions to both their Principles

⁵ This difficulty must not be confused with mere inability, owing to lack of figures or methods, to express our factors numerically. The difficulty is much more fundamental than that.

⁶ An interesting intermediate case of partial quantification should be noticed in passing. When trying to form an opinion about the effects on economic growth in the United States of a reduction of the income tax in the higher brackets we have to distinguish two things: the effect upon investment (“saving”) and the effect upon motivation. The first effect, given adequate data and also given agreement on certain points of theory (which seems unattainable just now) could be calculated to a nicety. But the second effect cannot; it must be left to (highly prejudiced) hunches or impressions that hardly deserve to be called “estimates.” More precisely, however, this is true only with respect to the net of this effect. Certain elements in it are also quantifiable. It need hardly be added that, giving in to human weakness, economists are prone to treat as nonexistent what is not quantifiable and sometimes even what is not measurable.

⁷ The problem is, of course, further complicated by the fact that unfavorable effects are compatible with positive observed rates of growth and favorable effects with negative ones.

⁸ To repeat, this is, of course, not the only phenomenon to watch. Moreover, processes in other countries were much more complex. And this was not overlooked by contemporaneous writers. Bodin, for example, did criticize the one-sided view of Malestroit but included the element stressed by the latter in his own analysis. He also included others. It would be quite wrong to aver that he propounded a strict quantity theory. All he did was state that the impact of the precious metals was the first item to consider in an explanation of that price revolution. Not even the late Lord Keynes or Mrs. Robinson would deny that.

⁹ That is to say, the quantity theorem is essentially static; in the equation MV = PT, all four quantities refer to one and the same point of time. Its contents may be enriched by “dynamizing” it, that is, by giving appropriately different time subscripts to the several quantities.

¹⁰ This is, after all, but a special case of a problem of general historical methodology of which historical determinism is the other side. It is, so it. seems to me, just as “speculative” and “unscientific” to equate the undetermined or at least undeterminable personal element to zero as it is to overemphasize it in the way of Carlyle. Only unbiased historical research can reveal its true contours. Hid I time, I might suggest particular methods for doing this. But the real difficulty is in getting that unbiased research. For it is inevitable that, at present more than ever, individual research workers should emotionally like one type of result and dislike another.