just to add, some writers distinguish between societies where slavery existed (almost every human society) and "slave societies", where "the definition of the r

just to add, some writers distinguish between societies where slavery existed (almost every human society) and "slave societies", where "the definition of the relationship between ownership and labor -- is defined by slavery". (see: http://www.theatlantic.com/personal/archive/2011/09/the-slave-society-defined/244581/ http://www.theatlantic.com/personal/archive/2011/09/the-slav...)