From these principles, and others which naturally flow from them, may a statesman steer a very certain course, towards bringing the rate of interest as low as the prosperity of trade requires, or the principles of double competition between borrowers and lenders will permit. ------------------------------------------------------------------------ CHAP. VIII. _Is the Rate of Interest the sure Barometer of the State of Commerce?_ Some political writers are fond of every expedient to reduce within a narrow compass many questions, which being involved in intricate combinations, cannot be reduced to one principle. This throws them into what I call systems; of which we have an example in the question now before us. There is nothing more difficult than to determine when commerce runs favourably, and when unfavourably for a nation. This would not be the case, were the rate of interest the just barometer of it. I have found it however advanced, that nothing more is necessary to be known, in order to estimate the relative profits upon the foreign trade of two nations, than to compare the common rate of interest in both, and to decide the preference in favour of that nation where it is found to be lowest. We may say of this proposition, as of the course of exchange; the lowness of interest and exchange are both exceedingly favourable to trade; but they are no adequate measure of the profits arising from it. The best argument in favour of this opinion with regard to interest is, that the nation which sells the cheapest at foreign markets is constantly preferred; and, consequently, where the use of money is the lowest, the merchant can sell the cheapest.