Page:Hull 1900 Petty's Place in the History of Economic Theory.djvu/15

Rh  did Boyle's, or Linnaeus Ray's, or as the application of the method of limits modified the Newtonian fluxions.

If we turn to the history of political arithmetic in England, we find the influence of Petty alone as clear and decisive as was the joint influence of Petty and Graunt upon vital statistics. Davenant declared that Petty first began the application of this art to the particular objects of revenue and trade, in which he had as yet been followed by very few. If there had been open to the industrious doctor such opportunities to examine the correspondence of Southwell, Williamson, Sir Peter Pett, Halley, and Justel as the student now enjoys, he might have been led to modify his belief that nobody but Gregory King and himself appreciated this side of Petty's activities. Yet it must be admitted that King and Davenant, working as they did under the direct influence of Petty upon the fuller data afforded by a new financial policy, brought the art to the highest pitch which it ever reached. Their followers, with the possible exception of Arthur Young, exaggerated its methodological fault of multiplying conjectural averages to secure aggregates instead of deducing the averages from aggregates directly enumerated; and when the income tax and the census of 1801 afforded more accurate estimates of national wealth and of population, political arithmetic was driven forever from its two chosen fields. It is probable, however, that the interest which it had excited and the suggestions which it had evolved contributed not a little towards making a census possible both in England and elsewhere.

  The content of Petty's work was more and more restricted by his method as fondness for terms of number, 