In her book The Cosmopolitan Tradition: A Noble but Flawed Ideal, Martha Nussbaum observes that nationalism is on the rise across the world. Over the last five years, nationalist parties that oppose free trade and freedom of movement have gone from fringe movements to mainstream parties. Nationalism negotiates people’s obligations toward one another based upon race, ethnicity, or even religion. By its very nature, nationalism always excludes some group of people deemed to be the “other.” On the other hand, cosmopolitanism encapsulates a comprehensive and varied set of beliefs. All cosmopolitans tether themselves to an axiomatic commitment that all human beings, regardless of race, religion, or political orientation, are part of one single universal community comprising the whole of humanity.

The Ancient Greek iconoclast Diogenes first uttered the word “cosmopolitan” in the fourth century BC. When asked from what city he hailed, he candidly replied that he was a citizen of the world, a cosmopolitan. The Stoics, a then‐​contemporary school of philosophy, latched onto the idea of a union of humanity taking priority over more localized matters such as ethnic or civic ties. The Stoics believed that every human being commanded respect by virtue of their rational capacities. Against most worldviews of their day, Stoics believed that barbarians, slaves, and women were all worthy of dignity. This tradition of cosmopolitanism filtered down throughout the ages thanks to Roman thinkers such as Cicero, the famous politician in the republican period, and Marcus Aurelius, who was dubbed by Machiavelli as the last good emperor of Rome. Subsequent thinkers such as Hugo Grotius and Adam Smith appropriated elements of the Stoic tradition in their theories of international justice.

As her book title suggests, Nussbaum admires this tradition of radical equality of dignity for all. Yet she believes there are some faulty assumptions nestled within the Stoic philosophy that stunt the development of a more robust and consistent cosmopolitanism that can be applied to our modern world. Globalization has made cosmopolitanism a necessity due to the increased interconnectivity of people from disparate nations.

The first two chapters deal with the tensions within ancient Stoicism that make it an untenable position to hold, even if the overall ideals of Stoicism are attractive in their expression of the human spirit. In these chapters, Nussbaum argues that the issues with Stoicism are twofold.

First, Stoics make a distinction between the duties of justice and duties of material aid, what Nussbaum refers to as a bifurcation of duties. Nussbaum believes there are first‐​and second‐​generation rights. First‐​generation rights consist of religious freedom and political liberty, while second‐​generation rights are social and economic goods. Nussbaum argues that both require considerable resources to uphold, therefore both are equally worthy of merit. Stoics mistakenly assume that first‐​generation rights are free to enforce. As Nussbaum points out, however, a legal system does not establish itself without considerable cost.

The second problem is that the Stoics believed in an overly demanding theory of human dignity, one in which material possessions are not required. When Alexander approached Diogenes and offered anything he wanted, Diogenes simply requested Alexander step out of his light. This story is representative of the Stoics’ opinions of material possessions: all a true Stoic needs is his dignity. Stoics do not adequately acknowledge the importance of material goods in allowing for a flourishing and virtuous life. One Stoic, Seneca, explained that if a slave has a free soul, his external slavery will not matter because he will be free internally. Nussbaum, along with most modern observers, find this position untenable. Even if one has a Herculean character, the throes of fortune and deprivation will damage one’s sense of dignity. Nussbaum claims that the Stoic belief in the indomitable human spirit is admirable but leads to many uncomfortable conclusions. For example, the Stoics view material wealth as a neutral good, not inherently bad or inherently good. But since for the Stoics virtue is all that is needed for a good life, longing for material goods is deemed a waste of time. This position, while principled, has perverse conclusions. Ancient Stoics condemn those in poverty as being poor of spirit simply for wanting a sufficiently comfortable life. This seems bizarre to the modern reader who is more sympathetic to poverty alleviation.

Yet I take issue with Nussbaum’s point about the similarity of first‐​and second‐​generation rights. Yes, first‐​generation rights require resources to uphold. In their ideal sense, however, they are at least impartial. They are afforded to all people equally, even though, in practice, this is more complicated. We all pay for first‐​generation rights through taxes and we all benefit from their upholding. Second‐​generation rights are only reserved for certain people, the poor and desperate. Thus, when someone puts resources toward a second‐​generation right, their duties are wholly toward another person, and they gain no value for themselves through contributing. Simply because two duties require resources to uphold does not mean they are fundamentally the same.

The next two chapters of Nussbaum’s work cover the thought of Hugo Grotius and Adam Smith who, in Nussbaum’s analysis, both worked toward a more compassionate and holistic cosmopolitanism than the rugged Stoics. Grotius imbued the Stoic tradition with an awareness and a respect for nations as loci of human autonomy, while Smith acknowledged the importance of material aid such as health and education as the preconditions for a flourishing life.

In the remaining chapters, Nussbaum turns her attention to policy in the modern world, in which she focuses more on principles that justify a framework of policies. After sketching the radical implications of universal humanity, she advocates for a noninterventionist approach to foreign policy. She also deems foreign aid as ineffective. She instead advises for cautious aid in critical areas but a strict avoidance of cultivating the tyranny of expertise described by economist William Easterly. Nussbaum does not entertain the idea that lowering tariffs could aid the developing world while not infringing upon any nation’s sovereignty.

Nussbaum sketches the importance of our shared humanity, only to quickly backtrack on specific areas such as immigration. Nussbaum believes that, as long as a nation does not actively exclude any particular religion or ethnicity, it is permissible to limit the number of immigrants entering a country and to demand they live under the rule and in accordance with a nation’s fundamental principles. Nussbaum never explains why nations ought to be permitted to restrict the number of immigrants entering besides a gesture toward national sovereignty. If immigrants can increase their wages by a factor of ten by merely crossing borders, does this concrete material benefit not supersede the abstract notions of the importance of sovereignty? Nussbaum also separates migrants into categories but does not explain why these categories matter.

Lastly, Nussbaum summarizes an idea she has defended for quite some time: the capabilities approach. Dissatisfied with traditional approaches to measuring well‐​being such as GDP, Nussbaum developed an approach that is more holistic. She lists 10 capabilities that political orders ought to be able to secure as a minimum for their inhabitants. These include life, bodily health, bodily integrity, senses, imagination and thought, emotions, practical reason, affiliation, other species, and play and control over one’s environment through political and material means. Reiterating her previous criticism of the Stoics on the bifurcation of duties, Nussbaum reaffirms civil and political rights equality with social and economic rights. Nussbaum acknowledges that the capabilities approach does not provide a rationale for other needs, such as national defense and freedom from corruption.

At first, an extensive list of state‐​provided services and support might seem like a daring proposition for libertarian readers. However, Nussbaum’s capabilities approach is a framework rather than a set of policy prescriptions. How these goods are provided is irrelevant. From this perspective, a market solution to the capabilities approach could be mustered.

Nussbaum adopts an interdisciplinary approach by using elements of philosophy, intellectual history, and international policy. This interdisciplinary focus holds her back from dedicating herself wholly to any particular issue. She is not writing a pure philosophy book on cosmopolitanism, nor is she writing an intellectual reception of the Stoics and, finally, she is not writing a book of policy recommendations. For anyone acquainted with any of these specific genres, Nussbaum’s work will likely seem cursory and overly broad. A lot of the book deals with brief, high‐​level overviews of ideas and concepts as opposed to rigorous academic debate.

But while Nussbaum’s work may lack focus at times, her holistic approach does yield novel ideas. She has written a highly readable and accessible work that is an excellent overview of Stoic ideals of cosmopolitanism and the impact it had on Enlightenment thinkers. While Nussbaum disagrees with the Stoic position, she shows an immense knowledge of each thinker she discusses, including not only their philosophical opinions but also how their personal life influenced their worldview. The policies Nussbaum puts forward are not radically new, but they are cautiously realistic. Overall, Nussbaum is not attempting to give a detailed answer as to how to tackle the international issues at hand. Instead, she is constructing a framework for policymakers to apply. Nussbaum’s capabilities approach provides a challenging framework for libertarians to move beyond a solely rights‐​oriented focus to include a vision of a flourishing life both at home and abroad.