During the last 50 years, a significant area of debate in political science has been over whether or not scholars of politics can differentiate between objective and subjective interests. Critical theorists have argued that ideology and class power can distort individuals' perceptions of their interests, thereby causing people to act against those interests. Conversely, those scholars committed to behavioral social science and neoliberalism have insisted that individuals are the best judges of their own interests, and that market-based systems of exchange provide the most efficient means for individuals to make sure their individual tastes and preferences are met. Dean Mathiowetz upends this debate by writing a conceptual history of interest in political theory that argues that this narrow understanding of interest as calculating self-regard is a recent development that displaced an older, juridical concept of interest. Juridical interest treats interest as a claim about the authoritative ties between a person and his or her property. Mathiowetz argues that while the calculating sense of interest attempts to foreclose debate about what a person's interests are by claiming that interest points to a preexisting psychological phenomenon, the juridical use of interest is a site of contestation, self-constitution, and action because it conceptualizes interest as a dispute over the application of a norm.

Mathiowetz begins by considering current uses of the term interest by such politically diverse individuals as Thomas Frank and Alan Greenspan, and observes that there is a tendency for political analysts to be surprised when the pursuit of self-interest leads to undesirable ends for the individuals acting in their interests. Simply put, if individuals pursue and achieve ends that they feel to be in their rational self-interest, why are they continually disappointed with the results? Mathiowetz contends that this disappointment is the result of a conceptual misunderstanding of what interests are. Political analysts tend to treat appeals to interest as statements of “what matters” for the actor. These appeals to interest normally occur at sites of political contestation. But the structure of the appeal to interest tends to foreclose the possibility of considering other courses of action.

The author argues that this feature of interest claims is a relatively recent way of thinking about the concept that is the result of the neoliberal premise that individuals are rational, self-regarding actors and that the most efficient way of enabling individuals to achieve their interests is through a market mechanism that allows individuals the autonomy to rank their preferences through exchange relations with other members of society. He argues, however, that there is an older understanding of interest that he traces to medieval property law. When interest is understood in this sense, it refers not to an individual's psychological preferences but to the legal and personal relationship between an individual and an object.

Next, Mathiowetz examines how the medieval juridical concept of interest was transformed in the early commercial era of the sixteenth century into the practice of charging interest upon a loan. In the Middle Ages, charging a fee to borrow money was impermissible as it was considered usury. But the Dutch jurist Leonard Lessius worked around this prohibition by arguing that money was a tool of business and that it should be adjudicated just as real property was according to the principle of id quod interest. The author draws upon this history to offer a correction to Albert Hirschman's thesis that the early modern financial development of charging interest on a loan led to the development of a psychological orientation toward benefit. Contra Hirschman, Mathiowetz argues that interest is not just a psychological disposition; it also denotes the idea of having a stake or a share in something.

Mathiowetz then brings his discussion of interest to seventeenth century political debates. He argues that the term interest moves from its original financial context into a political one because of the linguistic connection between the words state and estate in the political discourse of the seventeenth century. He traces the development of the juridical, antihumanist language of interest in the writings of Henri duc de Rohan and Marchamont Needham and in the Putney debates of the New Model Army. He argues that even when these political writers made an appeal to the interests of the polity, the appeals were contested.

In Chapter 4, Mathiowetz turns his attention to Hobbes and scholarship on Hobbes's theory of interest. Liberals and game theorists have read Hobbes as arguing that individual self-interest is at the base of political order. Against these readings, Mathiowetz insists that Hobbes is the consummate anti-interest theorist. Hobbes equates interest with the multitude, which, he argues, is incapable of governing itself. A significant part of his political project is to replace a politics of interests with one of propriety. As such, rather than reading Hobbes as saying that self-interest directs individuals to enter into a social contract, Mathiowetz argues that Hobbes's sovereign redirects individual desire for self-preservation toward the sovereign's goals and constitutes self-interest through the state.

Turning his attention toward Stephen Holmes's Passion and Constraint (1995), Mathiowetz then argues that Holmes's historiography of self-interest is primarily concerned with defending the contemporary, neoliberal use of the concept. According to Mathiowetz, Holmes ignores those elements in classical liberal thought that are concerned with processes of self-formation. By looking at how J. S. Mill grapples with extraeconomic institutions such as education and the law, Mathiowetz contends that the nature of the relationship between self-identity and its interests is open. Thus, even classical liberal appeals to interest are more about the process of identity formation than the product of calculating self-regard.

The book concludes by examining how the language of interests often confuses contemporary students of politics. Mathiowetz argues that despite their significant political differences, both the liberal and the critical theory understanding of interest tacitly accept a view of interest as essentially psychological. The recovery of the juridical sense of interest will enable scholars to see that interest does not refer to some preexisting mental substance. Instead, appeals to interest are speech acts that constitute the identity of political subjects. As such, political scientists should not conceive of interests as preexisting and fixed but, rather, as constituted through speech acts and as always open to contestation.

Mathiowetz's work is an important contribution to political science. Appeals to Interest is the best kind of conceptual history—one that critiques contemporary assumptions about the limits of our concepts and recovers from the past alternative understandings of concepts that enable us to think and act differently in the present. While I think that the author's recovery of the juridical concept of interest is potentially very useful to political science, my one concern is that he does not fully flesh out how this concept could be used in contemporary practice. I finished the book unclear about how, for example, Arthur Bentley's understanding of interest could be applied to contemporary debates about the objective voting interests of American working-class whites. However, as a work of historical conceptual analysis, this is a first-rate work that should receive a wide audience in the field.