economist like Von Thünen—with whose aims Petty's thought exhibits much affinity though he lacks Von Thünen's conspicuous patience—may make similar experiments upon a small scale. Most of us, however, must get on as best we may without any economic laboratory whatever. In this respect Petty was no exception. Experiment being impossible, he substituted what he called Political Arithmetick, a beginning of what is now called statistics. It was by no happy chance that he turned to this new device. He had a perfectly clear conception of the end which he desired to reach and of the means by which he proposed to reach it. "The Method I take," he says, "is not yet very usual; for instead of using only comparative and superlative Words, and intellectual Arguments, I have taken the course (as a Specimen of the Political Arithmetick I have longed aimed at) to express my self in terms of Number, Weight, or Measure; to use only Arguments of Sense, and to consider only such Causes, as have visible Foundations in Nature; leaving those that depend upon the mutable Minds, Opinions, Appetites, and Passions of particular Men, to the Consideration of others: Really professing my self as unable to speak satisfactorily upon those Grounds (if they may be call'd Grounds), as to foretel the cast of a Dye; to play well at Tennis, Billiards or Bowles, (without long practice,) by virtue of the most elaborate Conceptions that ever have been written De Projectilibus & Missilibus, or of the Angles of Incidence and Reflection[1]"
He even anticipated the modern conclusion that statistical investigation, applied to wisely selected circumstances, affords perhaps the best substitute for experimentation that is open to an economist. In this sense he says, in the preface to the "Political Anatomy of Ireland," "As Students in Medicine, practice their inquiries upon cheap and common Animals, and such whose actions they are best acquainted with, and where there is the least confusion and perplexure of Parts; I have chosen Ireland as such a Political Animal, who is scarce Twenty years old; where the Intrigue of State is not very complicate, and with which I have been conversant from an Embrion; and in which, if I have done amiss, the fault may be easily mended by another[2]." The obvious meaning is, not that
