Read together, these two books supply key empirical and conceptual insights that can deepen our understanding of the relations between borders and migration, a topic that has clear political and scholarly importance, especially in light of the ongoing refugee “crisis” in Europe. Yet each text examines its respective topic much more broadly, such that the intersection between them is narrower than one might expect. Despite this divergence, it is worth noting two basic commonalities before proceeding to a more detailed review of each text.

First, just as the contributors to Borderities and the Politics of Contemporary Mobile Borders argue that borders are not only found at the edge of the nation-state’s territory but are in fact ubiquitous and take place both within and beyond the lines marking out the territory, so does Thomas Nail in The Figure of the Migrant claim that “the twenty-first century will be the century of the migrant” and that “we are all becoming migrants” (p. 1). As such, both works seek to expand our understanding of what are borders and who are migrants. Second, both works challenge the assumed primacy of immobility, which treats movement as a deviation from the norm. Nail thus posits that “societies are dynamic processes engaged in continuously directing and circulating social life” (p. 4). This underpins his claim about the pervasiveness of the migrant, but also his key thesis of “expansion by expulsion.” Similarly, a core claim of Borderities is that the border itself is “mobile,” meaning that it is both “multi-situated and portable” (p. 13). As various contributors show, this means that the border takes place within and beyond the nation-state territory; that it is not fixed but relatively fluid; and that the border is even carried around in the form of the passport and embodied by the migrant as he or she moves through social space, encountering highly differentiated regimes of control that give relatively free passage to some but erect barriers to others.

If both works share a commitment to broadening our understanding of their respective subjects, they pursue this goal in contrasting ways and their analyses disclose markedly different insights. Nail offers a “philosophical history” of the migrant that attempts to explain the conditions under which the figure of the migrant has become possible. Although he does not say so explicitly, presumably what makes this history of the present “philosophical” is his attempt to “conceptualize the emergence of the historical conditions that gave rise to the types of social expulsion that define the migrant” (p. 5). In this sense, Nail seems to follow Gilles Deleuze and Félix Guattari (What Is Philosophy? 1994, 5)—key points of reference in this text—in approaching “philosophy” as the creation of concepts. For example, Chapter 1 aims to create a political concept of the migrant so that we can “understand the common social conditions and subject positions of a host of related mobile figures” (p. 11). Moreover, to do so, Nail coins two new terms: kinopolitics, or the “theory and analysis of social motion: the politics of movement” (p. 24), as well as pedetic force, or the autonomous motion invented by the various figures of the migrant in response to their expulsion.

The conceptual elegance of Nail’s analysis is outstanding: Social force, he argues, takes four forms, which in keeping with his emphasis on motion he labels centripetal, centrifugal, tensional, and elastic. Each assumes dominance (without replacing the others) in one of four historical periods—Neolithic, Ancient, Feudal, and Modern—and produces a distinctive figure of the migrant—nomad, barbarian, vagabond, and proletariat. Nail boldly asserts that “social expansion has always been predicated on the social expulsion of migrants” (p. 7), but each society does so by using a different form of kinopower—territorial, political, juridical, or economic—so that the nomad suffers territorial expulsion, the barbarian political expulsion, the vagabond juridical expulsion, and the proletariat economic expulsion.

As will already be evident from this presentation, the historical sweep of The Figure of the Migrant is ambitious, to say the least. Some readers may be deterred by this, but it is well to remember that this is a “philosophical history” that aims to conceptualize different forms of migration that continue to appear in the contemporary period. Taking a cue from Deleuze and Guattari, perhaps the best way to evaluate the concepts that Nail offers is to consider whether they can reveal anything “Interesting, Remarkable, or Important” (What Is Philosophy? 82). In one of several portions of the analysis that earn these descriptions, Nail treats both the “direct expulsion of indigenous farmers from public lands and the reappropriation of their labor by other means” in Mexico (p. 190), and the antimigrant operations in the United States as forms of centrifugal force. In Mexico, the form of social expansion by expulsion is internal, whereas in the United States it is external, but in both cases the expulsion is political and thus produces “Mexican barbarians,” who are deemed as threats to the United States (in part because of cultural and linguistic difference) and naturally inferior, as well as politically disenfranchised. Within this section, we find a particularly insightful comparison between barbarians arriving at the border of Rome in 376 and contemporary Mexican migrants, which for Nail raises the question, “When will the empire fall at the hands of a migrant revolution?” (p. 198)

The ambition and boldness of Nail’s study is undeniable, but Nail himself points to both the historical and contemporary limitations of the book in its concluding chapter. This is an important recognition by the author, but it does not diminish the risk that the book’s philosophical history will fail to satisfy either more historically inclined scholars or those with an interest primarily in contemporary migration. While the former will likely find the historical sections too brief and superficial, the latter may find themselves eager to reach Part IV (“Contemporary Migration: Mexico—United States”), only to wonder whether the contemporary analysis really needed so much historical background to support it. Still, if we judge the quality of a book by the debates and further research that it stimulates, the provocative and well-argued thesis of the book suggests that it will pass that test.

While the bulk of Nail’s study is (philosophical-) historical, the essays brought together in Borderities and the Politics of Contemporary Mobile Borders take a decidedly contemporary approach, as signaled by the book’s title. The volume comprises 15 chapters written largely but not exclusively by geographers. Nongeographers and those new to border studies will find the introductory chapter useful, however, as it explains the two “foundational paradigms” of contemporary border studies: that “debordering/rebordering processes are concomitant and happen simultaneously everywhere,” and that the “forms and functions of borders no longer coincide” (p. 4); hence, the idea of the mobile border mentioned in the title. The contributions to this work then explore these paradigms in a variety of empirical settings. For example, in an incredibly dense chapter (previously published elsewhere and delivered as a keynote at the conference that led to the edited volume), Saskia Sassen explores “subnational scalings” of global processes, which produce novel bordering capabilities that traverse “traditional borders” and are a function of the latter’s opening (p. 43). Examples of such processes include “regimes protecting firms’ trading rights” and “protections for threatened species whose habitats comprise more than one country” (p. 23). Next, Michael J. Strauss shows how states enhance their sovereignty and effectively expand their borders through the lease of land outside their territory (extraterritorial concessions). The resultant borders are fluid, shifting according to the evolving interests of states and the duration of arrangements that create the concessions. Well-known examples are the Guantanamo Bay and Hong Kong leases, but Strauss mentions many others, and also considers the emerging role of nonstate actors.

Other chapters that more obviously converge with the focus of Nail’s study highlight the mobility of the border by focusing on the passport as a technology of spatial control carried by the individual (“the border in the pocket”) and the “embodiment of the border” through the deployment of increasingly sophisticated technology to verify an individual’s identity (most notably biometrics and e-passports). Gabriel Popescu’s contribution also includes a critique of the so-called smart borders regime; he suggests that this “overreliance on technology … promotes a view of security as simply a technical problem … and assumes that the world’s problems can be addressed by bordering them away with the help of technology” (p. 111).

Perhaps one of the more thought-provoking contributions that this volume makes comes from the attention that several chapters pay to mapping. If borders are mobile and processual, the question of how to represent them cartographically is raised. For example, in examining the deaths of migrants in the Mediterranean Sea, Nicholas Lambert and Olivier Clochard consider how two- and three-dimensional maps that identify “border hotspots” (variously portrayed as cones, a wall, a whirlpool, and a mound) where migrants have lost their lives can “produce a new political and subjective outlook of Europe’s migratory border” (p. 126). Other chapters consider how to represent the spatiality of terrorist groups in a manner that captures their mobility, and how maps made by inhabitants of Zingonia, a suburban location in northern Italy that is inhabited predominantly by Senegalese migrants, can provide a “counter-image” of that place. The epilogue is a reflection by artist Ariane Littman on her various works that use maps of Jerusalem as the basis for installations, performances, and videos.

Borderities offers a smorgasbord of studies in areas as diverse as migration, trade, environmental protection, terrorism, and smuggling, and will for that reason prove valuable to those with an interest in borders generally. Yet for those studying migration, many of these inquiries will be only marginally valuable insofar as they illustrate the broader theoretical claims of the volume regarding the mobility of borders. This breadth also means that the pieces sometimes felt disparate, which the editors might have been remedied with a conclusion reflecting on the lessons learned for their concept of “borderity,” as well as some of its political and ethical implications.