is inevitable if we admit his premises of the identity of “instruments” and property, but this is an unreal identity.[643] “Natural” (φύσει) is the saving word in his argument, but “human” (ἄνθρωπος) refutes it, as the philosopher practically admits later. He now proceeds to ask the question whether this “natural” slave of his hypothesis actually exists, for whom such a relation is just, or whether all slavery is contrary to nature, as some allege. He answers in the affirmative. The principle of rule and subjection he declares to be a foundation law of all life.[644] Men are constituted for either condition from birth, and their development follows this natural bent.[645] This law may be observed in inanimate things,[646] in the natural subordinate relation of the body to the soul, of domestic animals to man, of female to male, of child to parent, and of subjects to rulers.[647] Thus all who are capable only of physical service hold the same relation to higher natures as the body holds to the soul, and are slaves by nature.[648] This is the only relation for which the slave is naturally fitted, since he can apprehend reason without himself possessing it, being midway between animals and truly rational men.[649] Usually also nature differentiates both the bodies and the souls of freemen and slaves, suiting them to their respective spheres and functions.[650] This relation of slavery, Aristotle argues, is not only natural and necessary, but also beneficial for those who are so constituted.[651] Just as the body is benefited by the rule of the soul, and domestic animals by the rule of man, so it is distinctly to the advantage of the “natural slave” to be ruled by a rational master. This is universally true, wherever one class of persons is as inferior to another as is the body to the soul.[652]