This adventurous impulse, a volatile compound of restlessness, curiosity and self-confidence, seems to fascinate Abulafia even though it thwarts scholarly explanation:

The motives behind this movement of people are hard to fathom. One historian of Polynesian navigation, David Lewis, identified a spirit of adventure – a “restless urge” – among the Polynesians, citing the Raiateans from Tahiti, who would go voyaging for several months, touring the islands of that part of the ocean. They were observed by Joseph Banks, Captain Cook’s scientific companion, so the evidence is late and somewhat circumstantial. David Lewis also pointed to the “proud self-respect” of the navigators, a pride that would prompt sailors to set out to sea in bad weather if, for instance, they saw that the natives of an island they were visiting were taking to the sea, even just to fish. This idea fits well with the concepts of honour and shame of which anthropologists studying these ocean societies have written.

The same could be said for the sturdy Portuguese mariners who gradually extended their reach along the African coast—where Portugal would soon establish a maritime empire of coastal enclaves ultimately reaching as far as Goa on the coast of India and Macao off the coast of China. This spirit of adventure, as real and elusive as quicksilver, seems to surge among different peoples in different eras, evaporating as quickly as it bubbles forth. For instance, take the ancient Greek colonists who settled Sicily and many other areas far from the Aegean, and established overland colonies as far east as modern Pakistan; the aforementioned Portuguese who pioneered “global” economic imperialism in both Asia and the Americas before sinking into early decay as larger, more sophisticated nations like Spain, Britain and the Netherlands outpaced them; the United States with its last-man-in scramble for Atlantic and Pacific colonial possessions, culminating in the Spanish-American War at the close of the nineteenth century. Ironically, it was the earliest European colonial power, the Portuguese, that would last longest in Africa and Asia, clinging to Goa, Angola and Mozambique long after the end of other, larger European colonial projects in the same areas.

The Renaissance and the Age of Enlightenment would see a similar effervescence in the spirit of adventure—and of inquiry—that would drive the first great wave of European maritime-based expansion. The next great surge would come during the Victorian era—a period of incredible confidence, sense of “civilizing” mission (usually conveniently matched with a sense of self-interest) and the same thirst for adventure and exploration that drove earlier explorers of the New World. We may be witnessing another surge of the same impulse today in a renewed interest in space exploration.

PART TWO of The Boundless Sea (“The Middle Ocean: the Indian Ocean and its Neighbours”), deals primarily with the extensive patterns of ocean commerce developed by sophisticated Asian cultures. Some of these were short-lived, like the massive Chinese commercial fleets that would trade as far afield as Africa during the Song dynasty. This was when the port city of Quanzhou, teeming with Arab, Indian and other merchants, as well as ethnic (Han) Chinese, was probably the most populous, sophisticated international trading center in the world. Other maritime commercial networks, notably those of sea-going Arab traders ranging from Africa to India and what are now Malaysia and Indonesia, would predate the Chinese initiative by centuries and endure well into the twentieth century.

In Part Three (“The Young Ocean: the Atlantic, 22,000 BC–AD 1500”), the author chronicles the very gradual and initially hesitant steps that would lead from the pre-Columbian forays of Vikings and others, nibbling on the margins of the New World, to full-scale discovery and colonization. This includes the first stirring of what would become a massive European trade in black slaves, initiated on the Guinea coast.

Part Four (“Oceans in Conversation, AD 1492–1900”) arrives in mid-book where most readers’ knowledge of exploration and colonialism begins: the great age of European discovery and settlement in the Americas, and the development of massive sea trade and commercial settlement in Asia and Africa. Here it is important to bear in mind that the early explorers of what came to be called the New World thought they were heading toward a world even older than Europe itself: the legendary treasure trove of the East Indies and the spice islands. Much of this history was made in a mental as well as maritime fog, quite by accident. Thus, a Portuguese expedition intended for India would result

…in the accidental discovery of Brazil in 1500 – a voyage that [albeit unwittingly] linked four continents. This linking of the oceans was completed remarkably quickly during the sixteenth century, once the routes from the Atlantic to the Pacific had been mapped out by pioneers such as Ferdinand Magellan, the Portuguese captain in the service of Spain, Juan Rodríguez Cabrillo, the Spanish discoverer of California, and Francis Drake, sailing in the service of England. The world, as a book describing Drake’s voyages proudly proclaimed, had now been “encompassed.” The linking of the oceans culminated in 1565 with the despatch of the first Manila galleon tying the western Pacific (and, beyond that, China) to Mexico and, ultimately, the Atlantic trade networks.

It is at this point that what a purist might call historical inevitability kicked in. A Europe that had already begun to outpace the Muslim world and other old kingdoms and empires of the East—even more so the far less advanced sub-Equatorial coasts of Africa—was now poised to control the first truly “global” economic age, which it did at an incredibly rapid rate between 1500 and 1800.

The fifth and final part of The Boundless Sea (“The Oceans Contained, AD 1850–2000”) takes up the age of continued colonial expansion, which, in tandem with the industrial revolution and the rise of nationalism, would shape the modern world—for both better and worse. Even as jingoist rivalry set European nations at odds with each other and in competition for overseas empires—“Continents Divided, Oceans Conjoined” in the words of a chapter title—the border contours we still see in most parts of the globe begin to emerge. These include the European-ruled colonies in Africa, Latin America, Asia and the Pacific that, even after independence, are shaped very much along the lines originally agreed to by rival colonial powers. And a lot more than borders were shaped; today’s “globalist” language of science, diplomacy, commerce, higher education and technology—not to mention the vocabulary and style of global pop culture—is English, the shared mother tongue of the biggest of the early colonial powers (Britain) and the biggest of the late colonial powers (the United States). Esperanto, to use a nautical analogy, seems to have sunk without a trace.

As to the literal “conjoining” of the oceans, nothing so much symbolizes this incredible achievement as two of the most inspired, successful feats of engineering ever undertaken by man: the Suez and Panama canals. Since the Widow of Windsor was alive when work was begun (and in the case of Suez, completed) on both canals, these two epic “globalist” achievements can be chalked up to the vision, know-how and self-confidence of the Victorian Age. As Abulafia points out,

Looking back, what is astonishing in the case of this [Suez] canal and the Panama Canal is the willingness of investors to place money in projects which would, at best, produce returns far in the future, assuming the project proved viable. This reveals deep-rooted optimism about the desirability, even inevitability, of progress, and of man’s mastery over nature.

TODAY, WHILE our knowledge and technical capability go beyond anything the Victorians—with the possible exception of Jules Verne—could dream of, our collective sense of optimism would seem to be evaporating at an alarming rate. Except for the lure of outer space, the mood in most of the advanced West is now one of inward-looking navel-gazing. An appetite for self-examination seems to have supplanted the appetite for discovery, opportunity and adventure in the world around us.

Although his tome occasionally reads like a series of strung-together lectures and articles, Abulafia never entirely loses sight of his leitmotif. He always writes gracefully and with a contagious enthusiasm for his subject. A descendant of Sephardic Jews who were expelled from Spain after the Reconquista, it is possible that some of his ancestors might have been among the many conversos who played a major part in the early Spanish settlement and development of Latin America and the Caribbean; he certainly writes about the world they helped to find and build with intuitive understanding as well as impressive scholarship.

One of the most ironic lessons one takes away from Abulafia’s epic account is that in the process of discovery, it was the explorers’ accidents and mistakes, not their intended objectives, real and imagined, that paid off most handsomely in the long run. No gold, silver or gems to speak of were ever found along the eastern coast of what would become the United States. But its colonization by Christian dissenters, farmers, merchants and tradesmen would evolve into the single mightiest nation in history—and a model, flawed as it may be, that people all over the world still look to. Most of the treasures of the Spanish West Indies dried up long ago and never contributed much to the people who lived there or the kind of society they passed on to their descendants. While it was the last thing that Columbus and his successors were looking for, it turns out that the real “wealth of the Indies” was to be found in its virgin soil and in the determination of pioneers looking for land to work and call their own—a place to well and truly “settle” in. This may be the greatest of all the achievements of those who conquered The Boundless Sea.