Solidarity remains a second- or perhaps third-tier concept in political theory, despite the attention it received from Richard Rorty and Jürgen Habermas in the last decades of the twentieth century. Not only must it compete with related concepts like friendship and fraternity, but when solidarity does emerge, discussions about it frequently become arguments about justice, as the question arises immediately: Solidarity toward what end?

Philosopher Sally Scholz's new book brings solidarity front and center as a moral and political concept in its own right. Concerned that scholars use solidarity in imprecise ways, thus diluting its meaning and causing confusion, her aim is twofold: first, to set forth a classification system of three levels and then three types of solidarity, and second, to provide a theory of one of those types, political solidarity. Scholz defines solidarity at the most general level as 1) a form of unity that 2) mediates between the individual and community and 3) entails moral obligations. She then identifies three types of solidarity at the second level of her system: social, civic, and political solidarities. Attachments like sympathy and camaraderie comprise the third level in her system. She classifies these bonds as “parasitical solidarity” since they do not entail moral obligations and, thus, are not really forms of solidarity.

Scholz's project of conceptual clarification is primarily aimed at the second level, distinguishing what she calls the “three basic forms” from one another (p. 17). Social solidarity has to do with group cohesiveness, whether that group is a family, passengers on a bus, a club, a racial or ethnic group, or spectators at a sporting event. Each of these is marked by a degree of interdependence based on shared interests, experiences, or consciousness, which then translate into varying degrees of moral obligations to other members of the group. Civic solidarity has to do with the unity and moral obligations among citizens of a political state—obligations, Scholz claims, that are generally fulfilled through the state itself. Here, she comes the closest to equating solidarity with justice, noting that while justice focuses on “the individual's claim against the community,” civic solidarity inverts this and focuses on the communal obligation to the individual (p. 29). Though she notes that social solidarity might be a basis for civic solidarity, she also claims that civic solidarity does not necessarily require social solidarity.

The third basic form, political solidarity, arises out of a conscious commitment on the part of individuals to challenge a perceived injustice. This is the unity found in social movements, and the bulk of the book is aimed at theorizing this bond by describing the types of obligations it entails, the forms it takes, and some of problems that it raises. Scholz acknowledges that this unity is context dependent, manifesting itself differently according to the injustice targeted, the structures at issue, the extent of an individual's commitment, and other factors. Yet she contends that a common form of unity marks these struggles, connecting participants to one another and setting them off from those opposed or indifferent to the movement. The conscious commitment to fight injustice is fundamental to her conception, for this commitment not only distinguishes political solidarity from the other types but also gives rise to the moral obligations that mark it as a true solidarity, rather than mere parasitic solidarity.

Political scientists and theorists will benefit from Scholz's careful conceptual distinctions and her clear definitions. Although the “levels” framework seems unnecessary, especially since the third level turns out not to be solidarity proper, clarifying the differences among social, civic, and political solidarities is an especially useful contribution. Scholz demonstrates this in her discussion of the relationship between the oppressed group and those who are not oppressed but who fight alongside them against injustice. She argues that accounts of this relationship tend to conflate social and political solidarity and are, thus, unable to offer a proper analysis of the role of those who are not themselves victims. Distinguishing different forms of unity addresses this failing by identifying a ground for collective action—political solidarity's commitment to fight a particular injustice—one that is not necessarily rooted in shared experience or identity. It is not always clear in this analysis whether Scholz is making an argument about the conceptual tools for analyzing movements or offering advice to movements themselves. In arguing against identity as the basis for movement membership, for example, she claims that an identity approach “limits the membership of the social movement” and also “risks contradicting solidarity” since individual freedom is lost (p. 130). She later adds that such identities are often the product of oppression, which may itself “make solidarity an impossibility” (p. 132). This is certainly true, and it is good advice for movement leaders, though it is not clear that either of these is a problem for conceptualizing solidarity per se.

Nonetheless, Scholz's conceptual categories could inform current debates about recognition and redistribution. Bringing her categories and this literature together would open up further inquiry into the relationships among social, civic, and political solidarity, even if they can be distinguished conceptually. For example, a claim for recognition could fruitfully be framed as a movement of political solidarity based on an unjust denial of social solidarity—that is, as a demand to be included as part of a collective “we,” rather than remain a marginalized other. Or, a demand for redistribution could be framed as a movement of political solidarity pressing a claim for civic solidarity—that is, for the state to make good on its obligation to a particular group. A theoretical engagement like this would also press the question of why a conscious commitment must be the ground for the obligations of political solidarity, as Scholz claims. There is “no inherent duty to join in political solidarity itself,” she argues, but once one has made a conscious commitment against a particular injustice, obligations follow (p. 254). In this way, she largely refrains from addressing the question of justice posed earlier, even though the answer to this question may already lie within her own framework: Perhaps social and civic solidarity themselves demand that we make a conscious commitment to join in political solidarity with others.