Throughout the Middle Ages, the petty kingdoms of Western Europe fought incessant wars with each other (and with the encroaching forces of Islam). These could be devastating but they were rarely more than local. The Reformation, and the Wars of Religion that it unleashed across the whole of Europe from the mid-sixteenth to the mid-seventeenth century, changed all that into a virtually incessant, almost global, conflagration. The most devastating of these conflicts, now known as the Thirty Years’ War, from 1618 until 1648, raged across the whole of central and eastern Europe drawing into its maw, at one time or another, all the major states of the continent from Spain to Sweden. The huge armies that it created left behind them vast tracts of the continent in smoldering ruins. The death toll has been calculated at 5.75 million, which, expressed as a percentage of the world’s population, is considerably greater than that of the First World War (Pinker 2011: 142). Millions more perished from famine and disease. When it was finally over, a third of the population of central Europe was dead. “Is it the history of snakes and tigers which I have just written?” asked Voltaire in astonishment on rereading his own description of all this butchery: “No, it is that of men. Tigers and snakes do not treat their own kind in that manner” (quoted in Hazard 1963: 395).

In 1648 an agreement between the various representatives of over two hundred political entities of one kind or another, was finally reached in the north-eastern German province of Westphalia. This did not result in a single agreement, but in two separate multilateral treaties (that of Münster signed in January 30 and Osnabrück in October 24); nor did it bring an immediate end to the war (the fighting in Germany alone dragged on for another nine years). But the “Peace of Westphalia,” as it has come to be known, marked a new beginning in inter-state relations in Europe. It was the first truly international gathering of European states. It was the first formally to recognize the existence of two new states: the United Netherlands which had, in effect, established its independence from Spain forty years earlier, and the Swiss Confederation, which now became a sovereign republic, independent of the Habsburg Empire; it also banished religion as a cause for any future conflict. Henceforth the sovereigns of Europe would decide how their subjects worshipped and no longer would European nations go to war because they disagreed over their understanding of God’s intentions for mankind. Most importantly, Westphalia was the first agreement between sovereign nations that aimed to create not another “breathing space of two gladiators” but, in the terms used by both treaties, to secure “a Christian universal, perpetual peace and friendship” between both Catholics and the various kinds of Protestant, for the “glory of God and the security of Christendom.” The key term here was “perpetual,” and in the attempt to create the necessary conditions for perpetual peace, Westphalia was responsible for raising the possibility (if nothing more) of what in 1802, Friedrich von Gentz, Prussian litterateur, Burke’s translator, former pupil of Kant and colleague of the Austrian statesman Prince Klemens von Metternich, called variously the “federal constitution of Europe,” the “general union,” and the “European League” (Gentz 1802: 11–15).¹ Gentz recognized that, even if Westphalia had not resulted in any “solid foundation for a public law of Europe,” it had given to the word “peace” a new meaning. No longer would it be thought of in terms of the end of one particular conflict, but as the end of all conflict.

To make this a reality, however, it would not be sufficient simply to re-order the balance of powers within Europe, as Westphalia had in effect done. It would not even be sufficient to establish, as Gentz had claimed it had, a new and regulated system of diplomatic relationships, governed, at least in theory, by a new system of “international law.” True, it could be argued that these had prevented a recurrence, at least before the outbreak of the Napoleonic Wars in 1799, of the kind of wholesale conflagration the Thirty Years’ War had been. But Westphalia had certainly not eliminated war as such. A true—which could only mean a perpetual—peace could not be achieved solely through treaties, or even by means of the minimally successful “balance of powers,” both of which assumed that sooner or later war would begin again. As the Swiss eighteenth-century diplomat Emer de Vattel pointed out, most states, even in the commercially orientated world of the late eighteenth century, had a very restricted sense of what “peace,” and in particular “perpetual peace,” was intended to mean. In most peace treaties, he commented wryly

This, however, supposed that a condition of perpetual peace was indeed a realizable human goal. That belief derived from an assumption, which had been a commonplace since at least Aristotle, that for humans, unlike other animals, peace was a final cause, and that warfare could only ever be an extreme measure to repair a disruption of the natural, and for the Christian, God-directed order. “War,” protested the Dutch humanist Desiderius Erasmus in 1517, “was not a necessary part of the natural or divine order.” It was merely a means, in an as yet humanly imperfect, but perfectible world, to an end. Indeed, he wrote, “Nature taught mankind to seek peace, and ensure it. She invites them to it by various allurements, she draws them to it by gentle violence, she compels them to it by the strong arm of necessity.” (Erasmus [1517] 1917: 8). One of the consequences, however, of the religious struggles that swept through Europe during the sixteenth and seventeenth centuries, was that many had come to the dismal conclusion that this could only ever be, at best, a pious illusion. Conflict for humans, as for most other animals, was the norm, peace merely a hard-won interlude between hostilities. The most powerful and influential proponent of this view was, of course, Thomas Hobbes. The natural state of man for Hobbes was famously one of “that condition which is called war, and such a war as is of every man against every man” (Hobbes [1651] 1996: 82). Peace was highly desirable, which is why men were prepared to surrender their right to governing themselves exactly as they wished, so as “to live peaceably among themselves”; but it remained always an artificial condition brought about by a collective act of will. And of course, could it be dissolved at any time.

In the relative calm that followed the end of the Thirty Years’ War, however, the Hobbesian view of the condition of humanity as locked in a condition of perpetual conflict, restrained only by formal covenant, which had itself to be enforced by the sword, came to seem unduly bleak. Most of the prominent natural-law theorists of the late seventeenth and eighteenth centuries were overwhelmingly concerned with the urgent need to find a remedy for what they generally saw as the unnatural condition of incessant human conflict. The only way to achieve this, they believed, was through a new and theoretically robust account of the “law of nations.” And to do this they had to offer a re-invigorated account of human sociability that Hobbes had largely dismissed as a fantasy of the despised “Schoolmen.” Samuel Pufendorf, Christian Wolff, and Emer de Vattel, while fully accepting Hobbes’ basic view of sociability as a response to human needs, rather than an innate desire, also rejected the supposition that it had arisen exclusively as a means of controlling the perpetual war “of all against all.” Most would have agreed, on this at least, with Jean-Jacques Rousseau that “man is naturally peaceful and fearful, faced with the slightest danger his first instinct is to flee.” (“Que l’état de guerre nait de l’état social” [1760], Rousseau 1964: 601). Only when flight was no longer an option did humans resort to violence. Certainly bellicosity, irascibility, and conflict between individuals were as natural to the human as they were to any other animal. But this was always a private matter. True warfare was of a different order. It was public. It was organized, involved multiple agents, fueled collective as well as individual passions and was invariably sustained even when the initial cause had passed. Only “the disposition reduced to action” as Rousseau phrased it, to destroy the enemy state “or at least to weaken it by every means possible” was “warfare properly speaking.” (“Que l’état de guerre nait de l’état social” [1760], in Rousseau 1964: 607). And this was clearly an unnatural condition. “If by the “natural state of man,” wrote Vattel, in repudiation of Hobbes, “we understand (as reason requires that we should) that state to which he is destined and called by his nature, peace should… be termed his natural state” (Vattel 2008: 651). For Vattel as for Rousseau, warfare, public warfare, was not an expression of human nature. It was rather a consequence of mankind’s decision to abandon his natural condition of lawlessness and to create another: the state. For Hobbes, of course, it followed that the relationship between states mirrored, if not precisely then in most significant respects, that which had once existed between individuals in the state of nature.² For the natural-law theorists of the eighteenth century this, too, offered an unacceptably irredeemable image of the human condition. If man had been truly, if admittedly only minimally, sociable in the state of nature, then surely that quality—which Pufendorf had dubbed socialitas—as a property of his being could not be erased when he entered civil society.

One of the most influential proponents of this view, was Christian Wolff (1679–1754), professor of mathematics and “natural philosophy” at the University of Halle, in the German state of Brandenburg-Prussia, known to his contemporaries as “our German Newton.” For Wolff it was inconceivable, without the presence of an effective pre-civil bond between persons—what in the eighteenth century went under the name of “sympathy” and we would call “empathy”—that individuals in the state of nature would have been able to create societies in the first place. In politics, as in ethics, we must all, he insisted, look upon others ...