I've thought a lot about this lately. Slavery keeps getting brought up and is recognized almost universally as an evil. The question rarely gets asked, what is slavery, and what actually makes one a slave. It's not strictly the absence of compensation for labor because technically speaking these people were usually provided housing, food, protection, etc. and for centuries those would be considered legitimate forms of compensation for labor and I would say still are. Its the lack of free will, however, that defines a slave, the inability to freely choose where you want to go, how, you choose to like your life and earn your living, how to raise your children and with whom. Probably worth thinking about when you have governments around the world telling you certain businesses are unessential, restricting travel, and taking your money (your tangible labor) and spending it frivolously in places that don't benefit you in any way.