In Soul of the Beast, John and his mates are captured and taken somewhere to be sold as slaves. What is a slave?
The usual concept of a slave is someone who is owned by another person, much like a horse or a dog. The slave has no rights and must do anything the slave owner tells him or her to do. The owner can punish the slave as often and as severely as he or she chooses. The owner can kill the slave for any and no reason. Using this definition, many people throughout history were in fact slaves even though they were called something else: