It is not surprising that such propositions examined in their truth appear in one respect arbitrary and in another tautological. But it is not thus that they are examined, and it is not thus that propositions of mathematics are ever examined, for their value lies solely in the service that they render. Certainly Ricardo's law relating to land of varying fertility is nothing but the definition of lands of various fertility, in the same way that Gresham's law relating to bad money is nothing but the definition of bad money. The same may be said of any other economic law, as, for example, that every protective tariff is destruction of riches, or that a demand for commodities is not a demand for labour, since these, like the preceding, are simply definitions of the protective tariff, of the demand for commodities, and of the demand for labour. And it could be proved of all of them that they are arbitrary, because the concepts of land, tariffs, commodities, money, and so on, are arbitrary, and because they become necessary only when that arbitrariness has been admitted as a postulate. But the same demonstration can be given of any theorem in Geometry; since it is not less arbitrary and tautological, that the measure of a quadrilateral should be equal to the base multiplied by the height, or that the sum of the squares of a cathetic should be equal to the square of the hypotenuse. This does not prevent Geometry from being Geometry, or negate the fact that without it we should not have been able to build the house in which we dwell, nor to measure this star upon which we live, nor the others that revolve around it or around which we revolve. Thus, it would be impossible to find one's way in empirical reality without these economic formulæ, and that would happen which happened when economic science was still in its infancy; namely, that by its means measures of government were adopted, which were admirably suited to produce in the highest degree those evils which it was thought could be avoided by its help, a misfortune of which the Spanish government in Lombardy or in the Province of Naples in the seventeenth century, with its _cries_ and its _pragmatics_ in economic and financial matters, has left most excellent examples. Or what happens now, when ignorance, or deceitful interest, which profits by ignorance, proposes or causes to be adopted ruinous measures under the appearance of _publica salus,_ arguing that they are good, or that they are good for different reasons than those for which they could be maintained. Such, for instance, would be the proposal for fresh expenditure on public works that are useless or of little use during a period of economic depression in a country, and instead of relieving, increase the general depression; or the increase of protective tariffs, when industrial progress is slow, which ought to encourage industry, but on the contrary produce an industry that is unstable and artificial, in