It begins to be clear why there are no societies based on barter. Such a society could only be one in which everybody was an inch away from everybody else's throat; but nonetheless hovering there, poised to strike but never actually striking, forever. True, barter does sometimes occur between people who do not consider each other strangers, but they're usually people who might as well be strangers- that is, who feel no sense of mutual responsibility or trust, or the desire to develop ongoing relations.