186 Reason and Its Rivals (ca. 1550– 1815)reason that the voluntary law is needed at all, Wolff stated, is because of “the
perverse customs of nations.” Here, the echo of the medieval substitution
theory is palpable. Th e voluntary law was seen as essentially a compromised
form of natural law— with the compromises made necessary by the many
imperfections of human life. Ideally, natural law would simply be applied in
its pure form to the relations between states. Enlightened nations will there-
fore make use of the voluntary law “only unwillingly,” when circumstances
do not permit the application of the necessary law.
Th e voluntary law, it is true, was not seen as fi xed or immutable in the
manner of natural law (i.e., of the necessary law of nations). It changes ac-
cording to prevailing earthly circumstances and consequently is man- made
in the immediate sense. But the principles that guide it— those of natural
law—are fi xed and immutable. So closely connected, in fact, was this volun-
tary law to the necessary law of nations that Wolff readily conceded that he
had no great quarrel with persons who regarded them as substantially the
same.
Wolff ’s voluntary law, then, had the interesting properties of being both
man- made in its immediate origin and universal in its application. Th is
made for a somewhat awkward mix. Judging from the man- made element, it
would appear that the voluntary law ought to be— as its very name implies—
contractual in character, as it was for Suárez and Grotius. But no. It was not
open to free negotiation and horse trading in the manner of a contract or a
treaty. It was too closely harnessed to natural law to allow for that. So the
voluntary law was not really contractual in nature in any signifi cant sense.
But nor was it quite like natural law, since it was man- made (at least in proxi-
mate terms) and alterable over time. It was therefore a sort of conceptual
amphibian— placed neatly between man- made customary law on the one
hand and natural law on the other, while being distinct from both.
In his discussion, Wolff gave a second— and instructively diff erent—
explanation of the voluntary law. Th is was in terms of what he called a “su-
preme state” (civitas maxima), which was a kind of great global republic
whose “citizens” were the various nations. Th is amounted to a direct applica-
tion to states of the Aristotelian concept of natural sociability. “Nature her-
self,” in Wolff ’s words, “has united all nations into a supreme state” for the
same purposes for which individuals had originally formed states: for security
and mutual protection. Th is supreme state is formed by “quasi- agreement”