dominion by means of servile subjection, this was introduced because of sin. But if we speak of dominion in so far as it relates to the function of advising and directing, it may in this sense be said to be natural.'[4] [Footnote 1: i. 96, 3.] [Footnote 2: _Ibid._, ad. 1.] [Footnote 3: i. 96, 4.] [Footnote 4: _De Reg. Prin._, iii. 9. This is one of the chapters the authorship of which is disputed.] St. Thomas was therefore willing to endorse the argument of St. Augustine that slavery was a result of sin; but he also admits the justice of Aristotle's reasoning on the subject. In the section of the _Summa_ where the question is discussed, whether the law of nations is the same as the natural law, one of the objections to be met is that 'Slavery among men is natural, for some are naturally slaves according to the philosopher. Now "slavery belongs to the law of nations," as Isidore states. Therefore the right of nations is a natural right.'[1] In answer to this objection St. Thomas draws the distinction between what is natural absolutely, and what is natural _secundum quid_, the passage which we have quoted in treating of property rights.[2] He then goes on to apply this distinction to the case of slavery. 'Considered absolutely, the fact that this particular man should be a slave rather than another man, is based, not on natural reason, but on some resultant utility, in that it is useful to this man to be ruled by a wise man, and to the latter to be helped by the former, as the philosopher states. Wherefore slavery which belongs to the law of nations is natural in the second way, but not in the first.'[3] It will be noted from this passage that St. Thomas partly admits, though not entirely, the opinion of Aristotle. In the _De Regimine Principum_ he goes much further in the direction of adopting the full Aristotelian theory: 'Nature decrees that there should be grades in men as in other things. We see this in the elements, a superior and an inferior; we see in every mixture that some one element predominates.... For we see this also in the relation of the body and the mind, and in the powers of the mind compared with one another; because some are ordained towards ordering and moving, such as the understanding and the will; others to serving. So should it be among men; and thus it is proved that some are slaves according to nature. Some lack reason through some defect of nature; and such ought to be subjected to servile works because they cannot use their reason, and this is called the natural law.'[4] In the same chapter the right of conquerors to enslave their conquered is referred to without comment, and therefore implicitly approved by the author. [Footnote 1: II. ii. 57, 3.] [Footnote 2: _Supra_, p. 64.] [Footnote 3: II. ii 57, ad. 2.] [Footnote 4: _De Reg. Prin._, ii. 10.]