Page:Sir William Petty - A Study in English Economic Literature - 1894.djvu/88

459] trouble to find out whether it was objectively true. When he asserts that the price of silver in Russia and in Peru is determined simply by the quantity of labor, it is almost certain that he confidently uses this illustration, without investigating its truth. Statements such as these are—purely a priori—he is constantly making without being aware that they are less trustworthy than what he reports from his own observation in France or in Holland.

As deductions of this kind have played so large a role in the science of economics, it is interesting to scrutinise them in the pages of Petty's works. His employment of deductive method is concerned in reducing complex facts to simplicity. He only means, he says, to consider "such causes as have visible foundations in nature." He does not intend to consider those causes "that depend upon the mutable minds, opinions, appetites, and passions of particular men." And again, he states that he only uses "arguments of sense." This gives his conception of nature. In order to reach certainty we must leave out all the causes which he has particularized as depending on the mutable properties of human nature. When we analyse these, we must disregard them, and what remains will be in every case the natural state of the object investigated. He shows how he applies this method in detail in the case of rent. The accidental causes which affect rent are enumerated. These are: public security, good administration of justice, pleasure and honor of having land, better titles, size of population. When all these have been accounted for, the only factor left is the land itself; or in other words, the indestructible powers of the