@Adamah... I am with you most of the time in many discussions since they make a lot of sense and are completely logical. However I must say that times have changed (like you also try to point out by letting our modern moral principles shine on the past episodes/stories of thousands of years ago). Slavery as we KNEW it back then is almost gone (though still around 27 million people are living as literal slaves)... however... in these modern times we are still in some OTHER ways slaves (even if you do not want to acknowledge it). Why? because debts make for a different relationship between humans: one becomes a "master" of the other untill the debt is payed off. (I know it is also a biblical phrase but in this case it makes a lot of sense).
A lot of slaves back in the old days became slaves because of debts... It is called Debt Bondage . they had debts they could not pay off and where therefore made slaves.
Wikipedia states about this type of slavery in Ancient Greece: The most onerous debt bondage was various forms of paramone, "indentured labor." As a matter of law, a person subjected toparamone was categorically free, and not a slave, but in practice his freedom was severely constrained by his servitude. [7] Solon's reforms occurred in the context of democratic politics at Athens that required clearer distinctions between "free" and "slave"; as a perverse consequence, chattel slavery increased. [8]
They came into dominion of other people. In our times it depends on the "taskmaster" you have debts to... if you have debts to the mafia (which I never advise! :D) and not able to pay back you would probably loose your life. You are literally a free man in that situation and yet you are not: not paying or doing stuff for them means death. Some other "taskmasters" are not that rigouriously... however... they make take everything away you previously owned: they might throw you out of your homes. Surely they were not slaves literaly but the outcome is, in modern way of seeing it, disastrous. Banks have thrown people on the streets, leaving them homeless. Lets be honest: the amount of debts people (and even complete countries) have is enormous. There are therefore many "slaves" in our time (not literally mind!). Slave means: UNFREE human. Freedom has a very brood meaning. Slavery also has a brood meaning these days. It is not all that black and white (litteraly :P) anymore.
One of the things that were typical for slaves was that they were OWNED... they had no own identity and did not own property. Now... can you really state that someone who has a shitload of debts really OWN's anything? That he is able to CHOOSE his own life? No... he isn't. So... litteraly he is NO slave but yet because of circumstances he is because he can not walk away from his problems (maybe not even caused by himself). Even children of someone who is in debt can be forced to pay off the debts of their parents or their (ex)spouse (in the situation their parents die)... this is even a law in some countries.
Now for the record: Am I stating that working for a boss is slavery? No I don't... I do not mean you are a slave of the "boss" you work for. What I DO say is that we are slaves of debtors who we owe money to. It is one of the reasons why we have to work our butts off: governments, banks etc etc etc all demand money to be able to "rule" or "regulate" a country. Disobedience leads to (legal) punishment. It is THEY we need to pay... the "boss" is giving us money for labour in order for us to pay off our debts. Please do not forget that for example governments can DEMAND money of us and can raise taxes without our consent and although we can object it most of the time does not help a bit. So as you see: although we have a choice most of us actually have not much of choice ;)