Mare Liberum’s influence and importance were—and remain—independent of that larger commentary, they cannot be fully understood outside of the argument of which they formed a part. Grotius defended the Dutch seizure of the Sta. Catarina on the basis of a set of natural laws, which he derived originally from the divine will.7 The two primary laws of nature were self-defense and self-preservation. He defined self-preservation as acquiring and retaining anything useful for life, a process which assumed that God had bestowed the gifts of his creation upon all human beings collectively but on none particularly: Only through physical seizure (possessio) leading to use (usus) could ownership (dominium) be derived. Two further laws, of inoffensiveness (harm no one) and abstinence (do not seize the possessions of others), set limits to these primary laws; from these followed two further laws of justice: that evil deeds should be punished and that good deeds should be rewarded (De Jure Praedae, pp. 8, 10, 11, 13, 15). Together, these laws provided the basis for Grotius’s judgment of the facts of Luso-Dutch relations in the East Indies. If it could be shown that the Portuguese had committed evil deeds against the Dutch and against their indigenous allies, and if it could be shown that van Heemskerck had engaged in a just war against the Portuguese captain of the Sta. Catarina, then his spoils taken in that war would be a legitimate prize for the corporate body on whose behalf he acted, the VOC itself.
The bulk of Grotius’s argument turned on the two issues of law and fact. In the first third of De Jure Praedae, he laid out the conditions under which booty might be justly seized by Christians from other Christians and the broader circumstances that defined a war between Christians as just. Having established the terms of law, he turned to matters of fact in a detailed narrative of relations since the Dutch revolt between the Dutch on one side and the Spanish and Portuguese on the other, to show that “[t]he latter … have invariably set an example of perfidy and cruelty; the Dutch, an example of clemency and good faith” (De Jure Praedae, p. 171). Then, in the twelfth chapter of his defense, Grotius went on to argue “that even if the war were a private war, it would be just, and the prize would be justly acquired by the Dutch East India Company” (De Jure Praedae, p. 216).
When Grotius came to publish that chapter as Mare Liberum, he made no reference to the case of the Sta. Catarina or to the supposed facts of Portuguese aggression and depredation in the East Indies. Instead, he prefaced his argument with a refutation of skepticism about the natural basis of moral distinctions (The Free Sea, pp. 5–6, below). Against the instrumentalist view that such distinctions had been invented solely to benefit the powerful in their rule over the powerless, Grotius affirmed that the laws of nature are the product of divine will and that they can be universally understood by the application of natural reason. He again argued that God had created the world in common for all humanity but that property could be acquired through human “labor and industry,” subject to two of the primary natural laws he had set down in De Jure Praedae: “that all surely might use common things without the damage of all and, for the rest, every man contented with his portion shall abstain from another’s” (The Free Sea, p. 6, below).
Freedom of navigation and trade (commeandi commercandique libertas) exemplified those principles, whether applied to particular communities or to the universal society of humanity. To support this contention, Grotius appealed to Greek and Roman literature, to Roman law (in particular, to Institutes, II. 1. 1 and Digest, I. 8. 4), and to sixteenth-century Spanish authorities, above all the Dominican theologian Francisco de Vitoria and his fellow Salamancan, the jurist Fernando Vázquez de Menchaca. A notable omission from his battery of authorities was Scripture, a resource that Grotius’s Scottish antagonist, William Welwod, would later exploit. However, by framing his argument in this way, Grotius could illustrate the obligations of natural (rather than revealed) religion, beyond the interpretive traditions of particular denominations, and show that even the juristic traditions of the Spanish monarchy (which since 1580 had included Portugal) opposed the Portuguese. His broader framing of the argument also ensured that Mare Liberum would be understood as a general statement of the right to freedom of trade and navigation. In this way, it sparked a wider and more enduring controversy regarding the foundations of international relations, the limits of national sovereignty, and the relationship between sovereignty (imperium) and possession (dominium) that would guarantee its lasting fame and notoriety.
Grotius broke down the Portuguese claim of exclusive access to the East Indies into three constituent parts: the right of possession, the right of navigation, and the right of trade. The Portuguese could claim no right of possession by virtue of first discovery, because the lands of the East Indies were not terra nullius (unpossessed land) but were in the possession of their native rulers. The fact that those rulers were “partly idolaters, partly Mahometans” did not invalidate their right to dominion (The Free Sea, p. 14, below): As Aquinas and Vitoria had argued (against earlier thinkers like Hostiensis and John Wycliffe), grace could not confer dominion. Nor were the peoples of Southeast Asia “out of their wits and insensible but ingenious and sharp-witted.” No assumptions of tutelage, or even appeals to Aristotelian conceptions of natural servitude, could therefore be employed to dispossess them, as Vitoria had likewise argued against the use of such arguments in the Americas (The Free Sea, p. 15, below). Papal donation could not have transferred dominium to the Portuguese because the pope possessed no temporal power, least of all over infidels (as, yet again, Vitoria had argued in relation to the New World). The only possible remaining claim was by “right of prey” (jure praedae) or conquest; however, that too was inapplicable to the Portuguese case, because the indigenous peoples had supplied no casus belli on which a claim to conquest in a just war could have been founded. With this reprise of four centuries of European arguments regarding the dispossession of the “barbarian,” Grotius left the Portuguese with no legitimate argument for possession. He then turned to their arguments for exclusive navigation and commerce.
Only at this point did Grotius directly address the subject of his title (Mare Liberum, The Free Sea) rather than his subtitle (De Jure quod Batavis Competit ad Indicana Commercio, The Right Which the Hollanders Ought to Have to the Indian Merchandise for Trading), as his argument shifted from rights over land to those over the sea. This distinction between territorial and maritime possession rested on a yet more fundamental difference between those things that could be appropriated and those that remained common by nature. If (as Grotius had argued in the body of De Jure Praedae) dominium could be derived only from use based on physical apprehension (possessio), only those things capable both of possession and of use could be appropriated from their pristine state of natural community, subject to the proviso that no other person should be harmed by the act of appropriation (an important limiting factor that permitted the private appropriation of the seashore but not at the expense of common access or use). On these grounds, Grotius argued that neither the Portuguese nor anyone else could claim exclusive possession of the ocean around and leading to the East Indies. Because the sea is fluid and ever changing, it cannot be possessed; because it (and its resources, such as fish) is apparently inexhaustible, it cannot be used: “[t]he sea therefore is in the number of things which are not in merchandise and trading, that is to say, cannot remain proper” (The Free Sea, p. 30, below). The land, by contrast, can be physically circumscribed, human labor does transform it, and its products are rendered private by their use. This fundamental contrast between the properties of sea and land would remain central to later conceptions of property within the natural-law tradition up to and beyond John Locke’s agriculturalist argument for appropriation, which similarly exempted “the Ocean, that great and still remaining Common of Mankind” (Locke, Second Treatise, § 30) from the possibility of exclusive possession.8
Yet if the Portuguese could claim no right of possession (dominium)
