ABSTRACT
Contemporary economists have only limited appreciation of the extent to which early practitioners recognized that, by their very nature, the problems in which they were interested required them to measure, quantify and enumerate. From the seventeenth century onwards inquiring minds had already learned to distrust information and ideas that derived from the then traditional qualitative approach to science, which described the sensations associated with objects and events. Much like Galileo, who saw the universe as “written in mathematical characters” (Galileo 1628:232), so William Petty, responding to the directives of nationalism and commerce, undertook “to express myself 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 considerations of others” (Petty 1690). He called his method “political arithmetick” and aimed not simply to record and describe reality in terms of numerical variables, but to use them as mental abstractions for the purpose of understanding whether there is a relationship between them and to use the information to accomplish some purpose.
