They clearly enunciated the doctrine that there is a natural division among human beings; that some are born to command and others to obey; that it is natural to some men to be masters and to others to be slaves; that each of these classes should fulfill the destiny which nature assigns.

The Greeks also recognized a difference between races and held that some were by nature fitted to serve as slaves, and others to command as masters.

The defenders of American slavery therefore found among the writings of the Greeks their chief arguments already stated in classic form.
Though the Romans added little to the theory of the fundamental problem involved, their history proved rich in practical experience.

There were times, in parts of the Roman Empire, when personal slavery either did not exist or was limited and insignificant in extent.

But the institution grew with Roman wars and conquests.