William Bramley/The Gods of Eden/21/214/3

Let us pretend that a chicken farmer was in the village market and wanted to trade for a basket of apples. He did not have his chickens with him, so he might write a note to the apple seller entitling the bearer of the note to come up to the farm at any time to pick out two healthy chickens. The chicken farmer would be able to walk away with his basket of apples and it would be up to the apple grower to visit the farm one day to redeem the note by getting his two chickens. As long as people have faith in the chicken farmer's ability to honor his notes, he will be able to use them for barter.