In the Laws, Plato describes civil war as “the greatest of all plagues” (Laws, 744d) which, according to David Lay Williams, is “the inevitable outcome of significant economic inequality” (p. 11). Williams uses this phrase as the title for his impressive intellectual history of economic inequality. Offering a thorough study of seven key figures in Western political thought, Williams sets an ambitious goal to demonstrate that inequality is not merely an epiphenomenon of some social structures or an easily ameliorated problem that just institutions are meant to address. Addressing the moral and political impact of inequality, according to Williams, is a significant driver of some of the most important political theories in the Western tradition. Turning to canonical thinkers, as Williams does, demonstrates the importance of understanding “how inequality affects psyches, social relationships, laws, policies, and institutions” (p. 318). In other words, some of the most prominent political thinkers understood that morality, psychology, religion, and education are perhaps even more essential than economics for comprehending the effects of economic inequality in society.

Beginning with a chapter on Plato, Williams offers a structured approach to unpacking what each thinker says about inequality. Each chapter begins with a description of the social context within which a writer developed his (they are all men) political theory and how that context likely shaped the respective account. Significant intellectual interlocuters or opponents help to establish the contextual history. Then, the relevant texts are scrutinized to divulge each theorist’s unique conception of inequality, its place in their work, and the specific solutions offered. Most of the thinkers discussed in the text not only identified the negative effects of poverty on people and communities, but they also reflected carefully on the wider impact of inequality: how it shaped laws; impacted social cohesion; incited wars; and led to the early death of huge portions of the population. As Williams notes, although secondary literature covers what a philosopher said about poverty, inequality per se is sometimes underappreciated.

After the chapter on Plato, Williams turns to Jesus of Nazareth, Thomas Hobbes, Jean-Jacques Rousseau, Adam Smith, John Stuart Mill, and Karl Marx, each with their own chapter. Jesus might appear as something of an anomaly, but Williams argues that the gospels present a compelling account not only of the hazards of poverty, but also of the sinfulness of wealth. Indeed, Williams argues that Jesus’s command to “love thy neighbor” could be interpreted as not sinning against them by acquiring wealth; similarly, loving one’s enemy exhorts the poor not to hate their wealthy neighbors (pp. 83–84).

Three dominant themes structure the book. First, the effects of inequality on the poor, including their life chances, their access to nonexploitative work, and their ability to participate in civil society. Although this last point – the relation between economic inequality and political equality – has been relatively well covered in political theory, Williams argues that the theorists presented in The Greatest of All Plagues demonstrate the systemic impossibility of political equality in the context of significant economic inequality.

The “corrupting effect of inequality on the rich themselves” (p. 315) is the second major theme. As Mill puts it: “inequalities in wealth […] have as pernicious an effect on those whom they seem to benefit, as upon those whom they apparently press hardest” (p. 217). Williams uses the Greek vice of pleonexia, the insatiable desire to have more, to illustrate how wealth not only makes people crave more wealth, but also corrupts social morals and the laws governing a polity. Karl Marx, like Plato, uses pleonexia to identify a core problem of capitalism: it creates the “context of limitless acquisitional possibilities” (p. 287). Consumed by greed, the wealthy embed lust for more into the economic and political structure.

The third theme pertains to the impact of inequality on political communities. As announced in the title, inequality has a vile, destructive effect on societies and social togetherness. Sufficientarians, who seem to be the foil for the book, hold that as long as everyone has sufficient resources to participate in political life, some inequality is allowed. According to Williams, they fail to grasp the important insights of the major political philosophers discussed in this book: that inequality divides political communities. Poverty alleviation alone cannot address the moral corruption of wealth and the divisive power of inequality. Plato, Jesus, Hobbes, Rousseau, Smith, Mill, and Marx recognize that inequality, not poverty, poses the most dangerous threat to social togetherness. Williams suggests: “We can only know whether we have ameliorated the problem of inequality by the degree to which we perceive citizens care more about, and are inclined less to exploit, one another” (p. 318).

The destructive potential of inequality on societies also suggests the role of governments. As Williams asserts in the chapter on Adam Smith, Smith’s various approaches to moderating economic inequality (including taxation and divine intervention) “suggest a palpable discomfort with economic inequality and some room around the edges for governments to use their limited authority to reduce the chasm between their wealthiest and poorest citizens” (p. 198). Each of the theorists advances substantive proposals for what ought to be done about inequality, including social reform, free education for the indigent, tax reform, property redistribution, and revolution.

Williams’s book offers the lesson that theoretical discussions can frame social and political problems like inequality in a way that can have direct and positive repercussions not only for political theory, but also the very people whose lived experience inspires the study. Williams himself seems to take this to heart from time to time throughout the text; he intersperses salient reflection on economic inequality or political polarization infecting contemporary social life and urges centering inequality to better conceptualize solutions.

Additional threads woven throughout the text help to hold this study of inequality in seven authors together. Given Williams’s past work on Rousseau, readers will not be surprised that the influence of earlier thinkers on Rousseau or Rousseau’s influence on later thinkers is a consistent theme and seems to motivate the selection of subjects. Similar weaving of influence occurs among and between the other theorists as well. Similarly, certain practices reappear to connect some of the thinkers. For instance, the biblical Jubilee laws (which required that property that had traded hands in the previous fifty years be returned), laws against usury, and education for virtue loop in and out of the seven theorists. The author also skillfully develops the contrasts, revealing subtle differences between the approaches to inequality and the solutions for amelioration.

Although Williams makes it clear that he is covering only economic inequality and not “social, political, gender, racial, religious, and other inequalities” (p. 7), it is worth questioning whether one can maintain such a focus, not only for the seven thinkers profiled in the book, but more generally. Indeed, Williams himself sometimes confronts the intersection of economic inequality with age, gender, and racial inequality. Children in eighteenth- and nineteenth-century England, for instance, often bore the weight of economic inequality through their forced labor, malnourishment, and early death, as Williams notes. Two prominent theorists whose work demonstrates the pernicious effects of economic inequality – Mary Wollstonecraft and Harriet Taylor Mill – are obvious choices for the study. Wollstonecraft engaged substantially with Rousseau’s work while also developing her own theory of economic inequality complete with remedies. Harriet Taylor Mill played an outsized role in the writing of John Stuart Mill’s Principles of Political Economy. She further argued for women’s complete economic and legal equality with men, reminiscent of many of the arguments that Williams identifies in other theorists. The absence of Wollstonecraft and Taylor Mill is noticeable and unfortunate.

Williams certainly accomplishes what he set out to do: to demonstrate that seven canonical thinkers carefully explain why economic inequality is morally and politically problematic. He does so in a thorough manner that situates each thinker in his respective time and social condition as well as intellectual circle. Williams also provides abundant, perhaps even overly abundant, textual evidence to demonstrate the focus on inequality in the thinkers he examines. The book would make a valuable contribution to a course on political theory focused on inequality. Indeed, at times, it reads a bit more like lecture notes guiding students through core texts, but that, too, speaks to Williams’s thorough approach.

The book contributes to global labour history by addressing the social history of the poor and working classes, the social psychology and moral appraisals of the wealthy and the poor in ancient and modern times, and the obligations of government to ameliorate inequality. Readers of the International Review of Social History will find much to appreciate in Williams’s book. In addition to reading canonical thinkers through the lens of inequality, Williams provides a valuable resource of primary material and secondary discussion rooted in the great books of western philosophy and the European Enlightenment.