The past decade has witnessed an unprecedented ascendancy of rights-based liberal individualism as the legitimating ideology of the capitalist world. No longer just the theme song of the American way of life, it has become the official creed of the European Union and the mobilizing doctrine of Western military intervention around the world, from the Middle East to the Balkans, from sub-Saharan Africa to the Caribbean. This is a discourse that links institutional and cultural features internal to the Atlantic states to postulated universal interests of humanity as a whole. All human beings, it argues, are individuals entitled to certain rights, and while the advanced polities of the West may respect a far richer and deeper range of these than anywhere else, liberals have a duty to the rest of humanity to advance and promote minimal human rights everywhere and to strike down those who would deny them. What are the historical sources of this outlook? It has long been believed that this strand of political thought derives from theories of Natural Law and associated conceptions of social contract dating back to the seventeenth century, above all in England—a tradition that combined, within a single framework, a universalist notion of the nature and entitlements of humanity with a specific normative theory of what might constitute a civilized polity for the advanced countries. Out of ideas of the individual moral agent, possessed of attributes common to all mankind, there developed—according to a standard schema—notions of government by consent and, eventually, agreed rules of international conduct.

Richard Tuck’s Rights of War and Peace is a work of brilliant iconoclasm that leaves little of this conventional view of the origins of modern liberalism standing. It starts by contrasting two quite different conceptions of warfare in the sixteenth century, embodied respectively in the Italian humanist Alberico Gentili, a Protestant exile who became Regius Professor of Civil Law at Oxford (‘one of the most important and interesting figures ever to teach at that university’) a year before the Armada, and his contemporary, the Spanish Thomist Luis de Molina, Professor of Philosophy and Theology at Évora (whose modern editor is Manuel Fraga Iribarne, founder of Spain’s current ruling party). Molina, an heir of mediaeval scholasticism, drew on traditions of Christian doctrine and Greek philosophy to set tight bounds around a permissible resort to arms—essentially, war was legitimate only if its aims were defensive or reparatory. Wars in pursuit of glory or pre-emptive attacks were expressly forbidden, and aggression against barbarians was unjustifiable.

Gentili, on the other hand, an admirer of Machiavelli and associate of Bacon, invoked Roman orators and historians to justify wars of self-preservation—in which each side would naturally claim its cause was just—that included not merely deliberate provocation of hostilities but a pre-emptive strike to cut down a potential enemy before it reached its prime. To this licence for military aggression within Europe, Gentili added a quite new one for colonial conquest outside it. War, he argued, could legitimately be waged on behalf of ‘human society’ as a whole, against those whose practices defied common morality, to punish them for their outrages. ‘The cause of the Spaniards is just when they make war upon the Indians, who practised abominable lewdness even with beasts, and who ate human flesh, slaying men for that purpose. For such sins are contrary to human nature, and the same is true of other sins recognized as such by all except haply by brutes and brutish men. Against such men, as Isocrates says, war is made as against brutes’. Not only this: colonial conquest was also perfectly in order, if lands were empty or unused. ‘The seizure of vacant places is regarded as a law of nature . . . Even though the lands belong to the sovereign of that territory, yet because of that law of nature which abhors a vacuum, they will fall to the lot of those who take them.’

It was this heritage that Hugo Grotius, the central figure of Tuck’s account, developed into a full-blown theory of international law. In doing so, he could draw on another source—the transformation of moral theory effected by late Renaissance sceptics like Montaigne and Charron, who had argued that wisdom lay in repudiation of all passionate ideological commitments, whether religious or patriotic, in the interests of a cool self-preservation. For Tuck, Grotius is the real founder of modern liberalism because it was he who turned this quietist moral stance into the theoretical basis of a positive political philosophy. In this enterprise, his starting-point was the assertion that there were two fundamental laws of nature: the right of every man to defend his life and avert any injury to it; and the right of each individual to obtain and keep for himself ‘those things which are useful to life’. Self-preservation takes precedence over the rule that we should not inflict harm on others. As Grotius put it: ‘by nature’s ordinance, each individual should be desirous of his own good fortune in preference to that of another’. The only natural basis for someone to help anyone else was the principle of returning like for like: punish those who injure you and reward those who assist you. Consequently, Grotius endorsed Horace’s famous maxim that ‘expediency is the mother of justice and equity’. As Tuck remarks, the new doctrine offered ‘an extremely minimal picture of the natural moral life’. But this thin sociability allowed Grotius to make his key theoretical move. Relations between natural individuals could be modelled on those between states, as sovereign powers whose interactions were governed by the moral parsimony of only the most restricted rules of international conduct.

This fateful equation, Tuck shows, did not spring out of mere logical rumination. It was a direct product of Grotius’s concern to justify Dutch commercial imperialism in Asia—his first major work being a treatise defending the hugely profitable seizure of a Portuguese bullion shipment by a captain of the East India Company, who was also his cousin, in 1603. If there was no ultimate ethical difference between individuals and states, then ‘private trading companies were as entitled to make war as the traditional sovereigns of Europe’. The way was open for plunder in the Indian Ocean and the seizure of forts in Amboyna and beyond. Nor was this all. States, conversely, enjoyed the same rights of retribution as individuals in a state of nature. The sociability postulated by Grotius might be thin, but it was universal, dictating a moral law applicable to all humanity, whose infractions it was not only legitimate but incumbent to punish, regardless of whether or not they harmed the power that exacted retribution for them. As Grotius forthrightly expressed it: ‘War is lawful against those who offend against Nature; which is contrary to the Opinion of . . . Molina and others, who seem to require, towards making a War just, that he who undertakes it be injured in himself, or in his State, and he has some jurisdiction over the Person against whom the War is made’.