should not do harm to
another. Secondly, because nature did not bring in the contrary; thus
we might say that for man to be naked is of the natural law because
nature did not give him clothes, but art invented them. In this sense
the possession of all things in common and universal freedom is
said to be of the natural law, because, to wit, the distinction of
possession and slavery were not brought in by nature, but devised by
human reason for the benefit of human life. Accordingly, the law of
nature was not changed in this respect, but by addition.'[1]

[Footnote 1: I. ii. 94, 5, ad. 3.]

AEgidius Romanus closely follows the teaching of his master on the
subject of slavery. 'What does AEgidius 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 AEgidius
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 gene