Montesquieu

Peoples who, like sava­ges, have few pro­ducts to trade, and orga­ni­zed peo­ples who have only two or three kinds, deal by exchange. Thus the Moors’ cara­vans which go to Timbuktu in the heart of Africa to bar­ter salt for gold have no need of money. The Moor puts his salt in a heap, the Negro his pow­der in ano­ther ; if there is not enough gold, the Moor takes back some salt, or the Negro adds some of his gold, until the par­ties agree.

But when a peo­ple tra­des a very large num­ber of pro­ducts, there must neces­sa­rily be some coin, because a metal that is easy to trans­port spa­res many expen­di­tu­res which one would be obli­ged to incur if eve­ry­thing was done by exchange.

As all nations have mutual needs, it often hap­pens that one of them wishes to have a very large num­ber of the other’s pro­ducts, and the lat­ter very few of theirs, whe­reas with res­pect to some other nation the situa­tion is the reverse ; but when nations have a coin, and pro­ceed by sale and pur­chase, those which take more pro­ducts set­tle up or pay the balance in sil­ver ; and the dif­fe­rence is that in the case of a pur­chase, the trade is made in pro­por­tion to the needs of the nation asking the most, and in an exchange the trade is made only to the extent of the needs of the nation asking the least, or else the it would be impos­si­ble for the lat­ter to set­tle his account.