In his excellent 1976 study of Montesquieu and the Old Regime, Mark Hulliung gives a vivid account of Montesquieu’s attitude toward “The World of Leviathans” encountered in the 18th century. In the course of his analysis Hulliung provides a commentary on the relationship between Grotius and Machiavelli, of the law of nations and realpolitik, that is startling in its implications:
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By Montesquieu’s day, the Leviathans which had arisen at the time of the Reformation were more menacing than ever. “Since Louis XIV,” he complained, “there is nothing but great wars: half of Europe against half of Europe,” a view historians have corroborated by referring to the Sun King’s final conflicts as “the first world wars.” . . .Leviathan was a predator intent on conquest, and everywhere it spied potential victims. There were other Leviathans it hoped eventually to subdue, and in the meantime it could feast on easier prey. To the Americas and the Orient it raced, knowing full well how vulnerable those territories were. A great age of imperialism was at hand as the struggles of the European Leviathans overflowed into the remote corners of the earth. . . .
Such was Montesquieu’s immediate “is” of international relations, the descriptive “is” preceding theoretical explanation and understanding. “Ought” follows quickly on its heels and assumes the form of a total rejection. Always morally outrageous, wars are never legitimate, except when fought in self-defense. A state may not attack until it has been attacked, unless a preventive war is its sole hope of survival. Lest prevention be construed as pretext for attack, Montesquieu spells out its proper implications: "small states have more often a right to declare war than great ones, because they are more often in the situation of being afraid of destruction." Once victorious, the state forced to conquer against its will remains bound by morality and may not fatten itself at the expense of the loser. Success creates no rights of rape and pillage, but the conquering state does incur additional duties. "The right of . . . conquest I define thus: a necessary, lawful, but unhappy power, which leaves the conqueror under a heavy obligation of repairing the injuries done to humanity."'
Sometimes a prohibition of gratuitous violence, sometimes a regulation of necessary force, the "ought" of international relations can always be traced back to one value source. "The right . . . of war is derived from necessity and strict justice." In international relations, as at every critical juncture, justice emerges as the inexpendable evaluative principle of Montesquieu's thought. . . .
"Love of country, throughout history," Montesquieu charged, "has been the source of the greatest crimes, because general virtues have been sacrificed to this particular virtue.” Unwilling to allow that love of family entails hatred of countrymen, he was also unwilling to allow that love of countrymen entails hatred of foreigners.
To say that justice is the only general virtue is, then, to interpret it as a rank-ordering device that puts the moral life of the group to the test, granting it everything except the right to victimize outsiders. Within a country, the legal system counteracts the moral liabilities which are inseparable from the moral assets of the group. Whenever familial ties or the bonds of friendship are manifest as an aggressive extended egotism, justice can be asserted through the realm of law. Within international politics, however, lawlessness abides, and each Leviathan is for itself. Hence Montesquieu's concept of justice as a kind of super-value situated above a ladder of particular virtues laden with the content of social and group relationships. Making certain each rung in the ladder gets its due, but no more, is the function of justice.
All we need add, now that the meaning of justice has been determined, is that this norm applies to all times and places. Unlike the Stoics of Hegel's interpretation, Montesquieu was not an advocate of a bogus world citizenship and universal ethics because the genuine citizenship and ethical life of the polis was no more. In Montesquieu 's opinion, the true heroism of civic virtue can no more excuse unnecessary killings than can the false heroism of honor.
Nor, however, was Montesquieu's opposition to war the product of cosmopolitan sentimentality. More than the philosophes, he knew how unreal "humanity" is, how real a Frenchman or Spaniard is. And he knew as well as Rousseau or Hegel how much the substance of ethical life belongs to the community and not to the world. Montesquieu's membership in the "party of humanity" diverges from the position of the philosophes in being entirely negative or remedial. His normative guidelines do no more than indicate what a polity may not do to its fellow polities. They give to the community what is the community's, most of all ethical life and the maximal content of justice, but take from it the sword of doom.
At last both the "is" and the "ought" of international relations are clarified. Destructive Leviathans constitute the "is," and an antidotal concept of justice constitutes the "ought." But instead of a solution, the upshot is a problem grown more acute than ever. How can the "is" be forestalled from shaking off the "ought"? How can "ought" be proven something more than Montesquieu's personal "ought"? A bond had to be formed between empirical and normative so that the "ought" could be solidly grounded in, and follow inescapably from, the "is."
Natural law philosophy, in alliance with the "law of nations" school, was the established genre in which a bridge had been built between "is" and "ought." But Montesquieu bitterly denounced the revitalized natural law/law of nations of Grotius, and for good reason. Norms had indeed been saved from irrelevant transcendence by the author of The Rights of War and Peace, but they were plunged so deeply into the empirical world as to be swallowed by it. Interpreters miss the mark, historically speaking, when they dwell on Grotius' belief in an a priori natural law. The keenest political minds of the old regime —Montesquieu and Rousseau — were surely correct in concentrating on the a posteriori version of Grotian natural law, for it was this which informed everything Grotius had to say about international relations. Rousseau stated the case against Grotius most succinctly: "His constant manner of reasoning is to establish right by fact. A more satisfactory mode might be employed, but none more favorable to tyrants."
At the start of his treatise, Grotius sets out to impose the yoke of legality upon masterless Leviathans, but by the end he has studded his performance with so many rationalizations and apologetics that Leviathan can find excuses for the worst of crimes. How is this possible? Purely intellectual factors provide part of the answer. An a posteriori determination of natural law and a prescriptive law of nations can be learned, Grotius argued, from the practices common to most civilized nations. But it was not the practices of contemporary powers to which he was attentive. Accepting the Renaissance penchant for classical pedantry, he turned antiquity upside down and shook examples of foreign politics from it. The momentous consequences of this procedure were not lost on Montesquieu.
The authors of our public law, guided by ancient histories, . . . have fallen into very great errors. They have adopted tyrannical and arbitrary principles, by supposing the conquerors to be invested with I know not what right to kill: from this they have drawn consequences as terrible as the very principle, and established maxims which the conquerors themselves, when possessed of the least grain of sense, never presumed to follow.
Machiavelli would have savored the irony of having Grotius, an international lawyer, as his accomplice. "Those cannot be considered wars in which no men are slain, cities plundered, or sovereignties overthrown," wrote the great Florentine who wanted nothing to do with the halfhearted bloodletting of modern times. Christianity was the culprit. Its influence on "the way of life and values of mankind" was evident in the regrettable contrast of the ancient and modern laws of nations. Greeks and Romans, unlike the moderns, were never squeamish in dealing with their victims. "Then, all who were vanquished in battle were either put to death or carried in perpetual slavery into the enemy's country where they spent the remainder of their lives in labor and misery. . . . But at present, those terrible apprehensions are in great measure dissipated and extinguished." Things had degenerated to such an impasse, the will to power was so enfeebled, that fighting a war was no longer a profitable venture.
The predilection of Grotius and his kind for antiquity could mean but one thing. Thinkers in the law of nations tradition were giving back to Machiavelli everything the modern age had denied him. Rights of conquest, enslavement, and pillage were affirmed. From one perspective a posteriori natural law had added "ought" to a preexistent, morally noxious "is"; from another perspective it went further by encouraging the development of an "is" far exceeding the evil already existent. Grotius had set out to subject a Machiavellian international reality to legality; he finished by making legalism an extension of Machiavellism. As Montesquieu insisted, the effect of international law was "to erect injustice into a system."
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