Ægidius Romanus closely follows the teaching of his master on the subject of slavery. 'What does Ægidius do? He unites Aristotle and St. Augustine against human liberty. He declares with the latter that man has lost the right of belonging to himself, since he has fallen from the primitive order established by God Himself in nature. He admits with Aristotle the existence of two races of men, the one designed for liberty, the other for servitude.... This is not all--to this servitude which he calls natural, the author joins another, purely legal, but which does not seem to him less just, namely, that which is founded on the right of war, and which obliges the conquered to become the slaves of the conquerors--to give up their liberty in exchange for their lives. Our author admits it is just in itself, because in his opinion it is useful to the defence of one's country; it excites warriors to courage by placing before their eyes the terrible consequences of cowardice.'[1] The teachings of St. Thomas and Ægidius were accepted by all the later scholastics.[2] Biel, whose opinion is always very valuable as being that of the last of a long line, says that there are three kinds of slaves--slaves of God, of sin, and of man. The first kind of slavery is wholly good, the second wholly bad, while the third, though not instituted by, is approved by the _jus gentium_. He proceeds to state the four ways in which a man may become enslaved: namely, _ex necessitate_, or by being born of a slave mother; _ex bello_, by being captured in war; _ex delicto_, or by sentence of the law in the case of certain crimes committed by freedmen; and _ex propria voluntate_, or by the sale of a man of himself into slavery.[3] [Footnote 1: Franck, _op. cit._, p. 90.] [Footnote 2: Franck, _op. cit._, p. 91.] [Footnote 3: Biel, _Inventarium seu Repertorium generale super qualuor libros Sententiarum_, iv. xv. I; and see Carletus, _Summa Angelica_, q. ccxii.]