From the Holy Quran 16:75:
Allah sets forth a parable: There is one who is a slave and is owned by another and has no power over anything; and there is one whom We have granted good provision Ourselves, of which he spends both secretly and openly. Can they be equal? All praise be to Allah. But most of them do not even know (this simple fact).
My reaction to the question was yes, they are both humans with souls: in what truly matters, they are equal. The Islamic Studies webpage suggests otherwise:
When the question was posed, obviously the mushriks could not say that the two men were equal. So some of them would have admitted that they were not equal, while the others would have kept quiet for fear that in case of admission, they would have to abide by its logical conclusion, that is, the admission of refutation of the doctrine of shirk.
I get the feeling I'm missing something important here.
Question: Are the slave and the slave owner equal?