172 Reason and Its Rivals (ca. 1550– 1815)diplomat and state counselor and also held a professorship in the law of na-
ture and nations at the University of Kiel in 1665— only the second such
academic chair to be created (the fi rst one, as noted later, had been estab-
lished a few years earlier at Heidelberg). His principal work, Dissertations on
the Law of Nature and of Nations, was published in 1676. Rachel was em-
phatic about the distinction between the law of nature and the law of na-
tions. Th e two diff er, he maintained, “by the whole heaven.” He expressly
lauded Grotius as the fi rst to perceive the distinction (being apparently ig-
norant of Suárez’s priority). Sometimes, he pointed out, a rule of the law of
nations, such as a treaty obligation, will simply reiterate or confi rm a rule of
natural law. Even then, though, it must be appreciated that two distinct
kinds of legal obligation exist— one under natural law and the other under
“the voluntary consent of nations.”
Th e human- created law of nations was needed, Rachel explained, to deal
with a key shortcoming of the natural law: its failure to provide solutions for
“the greater part of the businesses which free Nations enter on with one an-
other.” To fi ll that gap, the states themselves, “by their own discretion,” cre-
ated the voluntary law of nations. Th is law was defi ned by Rachel as “a law
developed by the consent or agreement, either expressly or tacitly given, of
many free nations, whereby for the sake of utility they are mutually bound
to one another.” As such, it was, in his words, “a species of Arbitrary
Law.” Subjects dealt with by this branch of law included (as they did for
Grotius) diplomatic relations and the conduct of war. In one interesting re-
spect, Rachel was a precursor of modern international law: he recommended
the establishment of an international tribunal for the settlement of disputes
between states.
Like Suárez and Grotius, Rachel held natural law to be more fundamental
than the voluntary law. For it was only through the force of natural law that
the voluntary law could be held to be binding. Most particularly, the legally
binding character of treaties was crucially dependent on the natural- law
principle of pacta sunt servanda. Natural law was therefore, in Rachel’s
words, the “remote cause” of a treaty obligation, with the treaty itself then
being the proximate cause of the specifi c obligations spelled out in it.
Rachel explicitly turned his attention, as Grotius had not, to the question
of whether this body of law ought more properly to be described as private
or public. Th is depended, he concluded, on whether one was concerned with
the content of the law or with the method of its creation. In terms of content