Putting Nature and Nations Asunder 153theory. At one point, he loyally described the ius gentium as a “derivation from
natural law.” But he immediately clouded the picture by conceding that there
were “occasions” when the ius gentium was not derived from natural law. He
proceeded to give four examples: inviolability of ambassadors, the establish-
ment of the sea as common property, the prohibition against enslaving pris-
oners of war, and the principle that it is “inexpedient to drive strangers out of
one’s land.” In those instances, the binding force of the ius gentium rested not
on natural law but instead on “the consent of the greater part of the world.”
Th is was clearly reminiscent of the dualistic thesis of Isidore of Seville— the
belief that the ius gentium has a diff erent content from natural law, that it
governs things that are outside the scope of natural law.
Vitoria then went on to note that, even if these ius gentium rules are not
actually derived from natural law, they nevertheless have a certain natural-
law fl avor. Th is is evident in the fact that they are (in his conception) binding
on the entire world, without exception— even on states whose governments
have not consented to them or accepted them in any way. Th is ius gentium
was therefore regarded by Vitoria as, in eff ect, international legislation, in
that it was based on the collective consent of the world at large. “[T]he consent
of the greater part of the world,” he explained, “is enough to make [a custom]
binding... even if a minority disagree.” Th e ius gentium consequently “does
not have the force merely of pacts or agreements between men, but has the
validity of a positive enactment,” that is, of enacted legislation.
All of this was a little hard to follow, and it must be said that Vitoria’s
thinking was not very coherent or consistent on this question. In the sev-
enteenth century, two later thinkers— Suárez and Grotius— were to bring a
greater mea sure of clarity to these premonitory sentiments voiced by Vitoria.
Th e Contribution of Francisco Suárez
Th e fi rst and most systematic case made during this period for a clear sepa-
ration between natural law and the ius gentium came from the pen of the
Jesuit scholar Francisco Suárez, who wrote in the late sixteenth and early
seventeenth centuries. Originally from Granada in Spain, he taught (like
so many) at the University of Salamanca, but moved to the University of
Coimbra in Portugal in 1597, where he gave a celebrated set of lectures on