174 Reason and Its Rivals (ca. 1550– 1815)Two notes of caution about the naturalist school are necessary at the outset.
Th e fi rst is that the naturalists did not actually hold natural law to be the
only law between states. What they held was that natural law was the only
law of general or universal application between states. Th ey accepted that
natural law could be supplemented by side arrangements between pairs or
groups of states on an ad hoc basis. But treaties were generally seen by natu-
ralist writers as being relatively unimportant in the grand scheme of things.
Th e second cautionary note about the naturalists is that, while they all
shared (by defi nition) the core belief that natural law is the only general body
of law between states, there was considerable room for variation as to what the
nature and content of natural law actually was. And many of the naturalist
writers— in fact, all of the best- known ones— did not share Hobbes’s ruth-
lessly stripped- down, asocial view of natural law. Th ey largely adhered instead
to the more conventional tradition of natural law— most notably, accepting
the venerable Aristotelian thesis of the natural sociability of humans.
An example of a naturalist writer who did share Hobbes’s own opinions
about natural law was the Dutch phi los o pher Baruch (or Benedict) Spinoza.
Spinoza was the very archetype of writers in the rationalist tradition of nat-
ural law. Where some writers, such as Grotius, had advanced mathematical
reasoning as their ideal, Spinoza came the closest of all to achieving it. His
famous treatise on Ethics (published posthumously in 1677) was written in a
severely geometrical style worthy of Euclid.
Spinoza was not a lawyer, but he turned his attention to po liti cal philoso-
phy in A Treatise on Religion and Politics (1670), followed by A Treatise on
Politics, published posthumously in 1677. Th ese writings were in a strongly
Hobbesian vein. He followed Hobbes in holding that only natural law gov-
erned relations between states. “[S]ince... the right of the sovereign is
simply the right of nature itself,” asserted Spinoza, “two states are in the
same relation to one another as two men in the condition of nature.” He
fl atly pronounced states to be “enemies by nature.” If anything, he was
even more radical than Hobbes in that he denied the existence of an absolute
duty to observe treaties. Once the motive for concluding an agreement
disappears— that is, once there ceases to be any advantage in adhering to a
treaty— a state has a “full right,” he maintained, to break it. Th e reason is
that a ruler owes a higher duty to his own subjects to protect their “safety and
advantage” than he does to fellow sovereigns to adhere to agreements.