Reason and Its Rivals (ca. 1550–1815) 141so much over the doings of craft y politicians— became stronger than ever.
Th e seventeenth and eigh teenth centuries became the golden age of natural-
law thought. Under the imposing heading of “systematic jurisprudence,” it
attracted the detailed attention of some of the fi nest minds of the era. Th ese
leading minds, incidentally, would nearly all come from lay rather than
clerical backgrounds— another revealing sign of the way in which the world
was changing.
It must be remembered, though, that natural law had a less prestigious
and less prominent partner: the ius gentium. Th e great story of this era, in
fact, would be the steady— and somewhat stealthy— gain of the ius gentium
over natural law, eventually to a position of equality and even of dominance.
Th e principal pioneers of this trend were a Spaniard, Francisco Suárez, and
a Dutchman, Hugo Grotius. Th ey certainly did not invent the basic idea that
relations between states are (or should be) governed by law. But they were the
ones who sculpted international law into substantially its modern form. Th ey
did this by loosening— though not severing— the close link between the two
bodies of law that had been forged in the Middle Ages. Th e eff ect was to make
international law, for the fi rst time, into a detailed body of specifi c rules
much like any other kind of law. Like so many pioneers, Suárez and Grotius
would have been dismayed at some of the directions in which their ideas
would later be taken. But that is a development for later in our story. For the
present, the focus is on the creation of international law in its modern sense.