as it draws gold or money from the earth or from other countries, poor in proportion as money leaves it. The wealth of a country must be estimated by the quantity of gold and silver in it."[1]
Schröder's book provoked a passionate attack from a French writer, Pierre Boisguillebert, in his "Dissertation on the Nature of Wealth" (1697), while in England the mercantilist advocates found in Sir William Petty a powerful opponent. Petty is by far the most important figure in political economy which the seventeenth century produced, although he wrote no large treatise specially concerned with economical matters. To him was first due the conception of labor as the ground or basis of value.
"Labor," he wrote, "is the father and active principle of wealth; lands are the mother."[2] And, again, in another place: "If a man can bring to London an ounce of silver out of the earth in Peru, in the same time that he can produce a bushel of corn, then one is the natural price of the other; now if by reason of new and more easie mines a man can get two ounces of silver as easily as formerly he did one, then Corn will be as cheap at ten shillings the bushel as it was before at five shillings, ceteris paribus."[3] He also anticipates, as the following passage will show, the theory of economic rent, its full conception only escaping him just as it escaped Adam Smith nearly a century later. "Suppose a man could with his own hands plant a certain scope of land with corn, could dig or plow, harrow, weed, reap, carry home, thresh and winnow so much of the husbandry as this land requires; and had withal seed wherewith to
