Montesquieu

The true maxim is to exclude no nation from one’s com­merce without very good rea­sons. The Japanese trade with only two nations, China and Holland. The Chinese receive a thou­sand per­cent pro­fit on sugar, and some­ti­mes just as much on the return ship­ment.1 The Dutch make approxi­ma­tely equal pro­fits. Every nation that beha­ves accor­ding to Japanese maxims will neces­sa­rily be chea­ted. It is com­pe­ti­tion that sets a fair price on mer­chan­dise and esta­bli­shes true rela­tions among them.

Even less must a state res­trict itself to sel­ling its pro­ducts to a sin­gle nation under pre­text that she will take all of them at a cer­tain price. The Polish made such a deal for their grain with the city of Danzig ; seve­ral kings in the Indies have simi­lar contracts for spi­ces with the Dutch.2 These conven­tions are the lot of a poor nation which is willing to give up the hope of get­ting rich pro­vi­ded she has an assu­red sub­sis­tence, or of nations whose ser­vi­tude consists in sacri­fi­cing the use of the things which nature had pro­vi­ded them, or making a disad­van­ta­geous trade.

Father du Halde, vol. II, p. 170.

This was first established by the Portuguese (Voyage de François Pyrard, ch. xv, part 2).