It is the principle of voluntary action versus physical coercion or compulsion. On the way north one of the raiders cut off her finger with a blunt knife when she tried to resist being raped. She was emancipated by the efforts of CSI in March of 2000. Nyadeng's story is one of thousands of stories that go on today in Africa. A slave is an innocent individual who does not act by of voluntary choice, but under compulsion, and the threat of physical coercion.
Slavery is a immoral, because it is a violation of the enslaved person's individual rights.
In the year 2000, millions of human beings are forced to lead lives as slaves. Typically, the market value of their work is many times greater then the sum of the money borrowed. Under the setup, they may never be able to repay the load during their lifetime. Child slaves are forced to work in dangerous conditions suitable only for adults, or as sex slaves, against their will. All forms of slavery are all clear violations of the principle of individual rights.