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Evocations and invocations of solidarity in public debates are many and eclectic. In politics, it is frequently used to justify extended social rights such as French and Quebec social security. During the COVID-19 pandemic, liberal welfare states like the U.K. with its National Health Service used the notion of solidarity to call for unity – in the sense of social cohesion. Political activists use solidarity to describe disparate practices at various scales, especially at the sub-state level of nationalist and independence movements (Tiryakian & Morgan 2014 : 256‑62) and in international contexts to express the idea of reciprocity, particularly between European states[1].

As many authors have pointed out (Alexander 2014; Reynolds 2014 : 1; Stjernø 2009 : 20; Bayertz 1998 : 293; Scholz 2008 : 10), this profusion contrasts with the discreet place solidarity takes in the literature of contemporary political philosophy. Since the 1970s, the discipline has increasingly focused on the concept of justice, often viewing the welfare state as the preferred means of achieving it (Kersbergen & Vis 2013 : 31-52). Much of the current literature does not seek to measure or compare different conceptions of solidarity but to evaluate the welfare state and its effectiveness in reducing poverty and inequality[2]. Unlike other moral concepts in the history of political ideas, such as liberty or equality, solidarity is not framed in systemic political theories[3].

Solidarity deserves a prime spot in political philosophy because it is the backbone of political action. With its unmatched ability to inspire and motivate, solidarity has proven to be a game-changer in social movements (Scholz 2008). However, solidarity is not just a buzzword; it allows us to contemplate the intricate web of connections that binds us all together (Blais 2007), especially during times of crisis, like the COVID-19 health crisis. Therefore, it is essential to acknowledge the significance of solidarity and its role in shaping our society. Although its potential relevance to political science, political scientists, theorists, and philosophers seem to avoid using the term "solidarity" and instead elude any definitional discussion and normative implications of the concept, confining it solely to the field of sociology[4]. Contemporary political science literature appears to label solidarity as a useless, premodern concept. So, why is it so tricky to comprehend solidarity as a political ideal? Are there legitimate reasons why present-day political science disregards the concept of solidarity, and if so, what are they?

I argue that it is present, even if only implicitly so. There are connections between solidarity and notions linked to mutual aid (Katz 1981), such as equity, reciprocity, and the fight against inequalities[5]. All of this prompts the inquiry: Beyond the sociological elucidations concerning the organization of knowledge production, dissemination, and conservation, are there theoretical underpinnings that elucidate the divergence of political philosophy from the notion of solidarity? This question requires going back upstream of our issue to find answers. Rather than comparing solidarity with justice and reconstructing a posteriori the reasons that determine the relevance of justice in the context of a given problem – which would be the topic of an article in itself – it seems interesting to take a step back to get a big picture of solidarity and liberalism. Can we find salient components of solidarity that contest central aspects of contemporary liberalism?

I will not provide an exhaustive review of solidarity or liberalism here. The objective of this article is to open a discussion on solidarity as a valuable political ideal in contemporary philosophy. To answer our issue, I would like to test an idea mentioned by various authors who have worked on the concept of solidarity. There is an incompatibility between solidarity and specific aspects of liberalism, which can be the reason why some contemporary liberals see positively "the dissolution of solidarity, not its maintenance or creation" (Alexander 2014 : 303). As Bayertz says, "One of the reasons behind this theoretical neglect is the fact that positive obligations to act, as the term solidarity implies, are difficult to incorporate within mainstream ethical and political thought" (1999 : 4). This so-called mainstream ethical should be understood as some specific aspect of contemporary liberalism, which has

a fundamentally defensive orientation: [it aims] primarily to ward off dangers to the individual accruing from competition with other individuals, the maelstrom of social conformity, or the powers of the State. Justifying individual rights of freedom has become a chief task of ethics; institutionally safeguarding them has become a chief task of politics and law.

Bayertz 1999 : 4

Solidarity creates individual obligations and anchors these obligations in a particularistic vision of the world: solidarity happens between members of a specific group and, implicitly or explicitly, against its non-members (Bayertz 1999 : 4). This particularistic vision of the world could challenge the good old priority of justice over goodness, which is an essential issue for non-perfectionist liberalism.

In what follows, I first discuss the elements that constitute solidarity as defined by the solidaristes of 19th-century France. In what way do solidaristes offer a concept covering something different from justice or charity? Then I focus on the origin of solidaristic constraint, a central concern in this discussion. I confront this element with two popular conceptions of individual liberty: negative liberty (Berlin 1969) and autonomy (Kymlicka 2015; Raz 1995). I demonstrate that the constraining aspect of solidarity raises specific tensions between these two forms of liberty. Finally, I test the compatibility of solidarity and individual liberty with a more suitable conceptualization of liberty: non-domination. From this discussion, two critical definitional aspects emerge — the particularistic dimension and the constraining dimension of solidarity – that come into play with reconciling solidarity and liberalism.

Solidarity among the French Solidaristes

What is solidarity?

To understand the theoretical reasons behind the abandonment of solidarity, we must determine whether it can be considered a specific concept in political philosophy. What issues does a definitional attempt of solidarity raise for political philosophy?

First, it is essential to note two solidarity dimensions: factual and normative (Bayertz 1999 : 3; Tiedemann 2018 : 1). Solidarity encompasses a range of mutual aid practices – such as community funds and insurance – and a desirable mode of mutual aid (Tiedemann 2018 : 1), as theorized by figures like Charles Fourier. He imagined an optimal architecture for promoting solidarity, called the phalanstère (Blais 2007 : 76). This imposing building was designed to encourage a sense of belonging and mutual help through specific arrangements of housing and services. If solidarity is merely a fact, there is no need to demand it; if it is desirable, we must find ways to promote it. Most authors agree that solidarity is both descriptive and normative simultaneously (Tiedemann 2018).

Moreover, solidarity remains closely related today to concepts used in sociology, such as social cooperation (Bayertz 1999 : 3) and social cohesion (Forsé & Parodi 2009), making it less potent for normative claims than ideal concepts like justice. Therefore, the challenge of defining political philosophy involves clarifying the normative dimension of solidarity without neglecting its empirical dimension (sociological interdependence).

Another reason for abandoning solidarity is the intense conceptual competition to describe similar phenomena. Concepts such as charity, justice, or even care could better describe assistance than solidarity. Consider justice. Rawlsian theory of justice has significantly influenced contemporary political philosophy, proposing a political organization of assistance. A just society is one where assistance is organized on reciprocity. Rawls avoids defining solidarity and distinguishes it from justice. For Rawls, solidarity (or "fraternity") is a vague concept that precedes justice and holds society together (Munoz-Darde 2018). Justice describes a mode of redistributing primary goods according to equity, whereas solidarity represents something broader—related to tolerance, equality, and reciprocity (Kymlicka 2015 : 4)—than the material redistribution of primary goods.

Some authors base solidarity on sharing common objectives or a common good within a group, making interdependence a duty towards the group (Löschke 2018 : 271). Because we need others to achieve this common good, we are committed to one another. This feature distinguishes solidarity from donation and charity, which are one-off individual actions without long-term commitment and without requiring a common good or a shared conception of what constitutes a good life.

The commitment generated by political solidarity depends on the form of the common good. The obligation can be legal, as was the case when the Romans used the word solidarity (solidum) to describe the responsibility of a group of debtors towards their creditors. It can also be ethical (Wiggins 2009). In this perspective, philosopher Pierre Leroux believes that solidarity is not necessarily a moral duty linked to Christian charity (Leroux 1840). This ethical obligation can be deontological to protect individuals from the law of the strongest (Wiggins 2009). However, some authors view it as a positive obligation (Fouillé 1885) based on prudence (Tiedemann 2018 : 1). If I do not engage in reciprocity when I am not vulnerable, I may face a refusal of mutual aid when my situation changes and I find myself in need.

From this viewpoint, solidarity is not without limits since it revolves around a common good, which may differ from one political community to another, but can also be a global common good. Thus, while some authors consider solidarity a universal value (Foot 2002; Wiggins 2009), most assume that solidarity always has limitations (Bayertz 1999; Heyd 2007; Kymlicka 2015; Löschke 2018; Rorty 1989; Tiedemann 2018). This commitment suggests that solidarity cannot be neutral and seems more like a perfectionist idea. Being in solidarity with someone is not an abstract principled stand—e.g., humanitarian aid—but a constraining commitment to a specific achievement.

However, this limitation can also be a global common good or can be formulated differently than using a common good. We can simply describe it as a sense of belonging to a group (Bayertz 1999; Sandel 2010). We feel closer to some humans than others for various reasons related to lineage, culture, history, shared values, and norms (Miller 1995) or because we experience the same oppressed condition (Scholz 2008).

Solidarity thus creates a boundary between an "us" and a "them" (Tiedemann 2018). Those in solidarity with each other are not in solidarity with the "others." This aspect raises essential questions about the constitution of this "we," its legitimacy, and the normative burden it imposes on both the members of that "we" and the "others," who are de facto excluded. How can we justify a moral, ethical, or political demand that is more important for some humans—those included in the "we"—than for others? We might think liberal democracy provides sufficient ethical guidance to organize living together and mutual aid without promoting an ambiguous conception of solidarity. Jacob T. Levy (2017) argues that solidarity is dangerous when understood as fraternity because it is based on a pre-political and anti-democratic mutual help conception.

Constraint and solidarity

We must return to the 19th century to find the basic idea of conceiving solidarity as a political we-concept[6]. The Western version of solidarity—that we use today, as in the introductory examples—seems to have first developed in France during the 1789 revolution (Brand 2005 : 43) before spreading to the rest of Europe in the 19th century.[7] Thinkers who worked on solidarity were called "les solidaristes." They theorized solidarity within nascent sociology and the young French Third Republic. They designed solidarity as a descriptive concept resulting from a positivist and organicist reading of the social world. A famous example of such an organicist vision is that of Émile Durkheim in De la division du travail social (Durkheim 2007 [1893]).

During this period, the politician and lawyer Léon Bourgeois offered the first attempt at a theoretical formulation of political solidarity in a book entitled Solidarité in 1896. The challenge for solidaristes like him was to propose a political justification for the constraint exerted by the State. Such constraint was required to organize public policies to lessen the human cost of industrialization. Solidaristes were secular republicans (laïcs) and eager to create political tools for justifying the welfare state without the Catholic moral concept of charity. He also focused on preserving the liberal achievements of the French Revolution, especially private property. That is why it is crucial for him that solidarity differs from collectivist socialism (Blais 2007 : 27).

To accomplish this, Léon Bourgeois proposes a contractual justification of solidarity. Even if we do not choose where we live, since birth, we benefit from other humans: our parents feed us and help us grow, and our community teaches us fundamental knowledge—mathematics, writing, speaking skills, history, etc. Since birth, we have been debtors to all humans who made our wealth possible. This social debt must constrain us, says Bourgeois (Blais 2007 : 34).

Solidarity is undoubtedly necessary—the interdependence between humans is natural and inevitable—however, collective choices can shape this interdependence and steer individual commitments. These collective choices must be subjected to moral or political justifications.

This intuition that solidarity constraint is still present and influential in literature. Agnes Tam sees solidarity as a we-reasoning group with an authoritative nature, sufficient to generate submission (2020). This constraint caused by solidarity raises the essential question of legitimacy. What are the conditions for solidarity being legitimate? Let us see how solidaristes legitimize solidarity as a constraining ideal and how this constraining dimension can challenge two specific liberal approaches to liberty.

Solidarity and Liberalism: the tensions between individual liberty and solidarity constraint

Solidarity and the Justification of Constraint

To justify the constraining dimension of solidarity, Léon Bourgeois develops two ideas. As we mentioned, he proposes seeing solidarity as a social debt owed to our ancestors as heirs to the wealth they bequeathed to us and as a debt owed to our contemporaries associated with producing the common good (Blais 2007 : 34). For Léon Bourgeois, this debt implies everyone's duty to contribute at least as much as what they have received as a legacy. Thus, since from our birth, we are dependent on others, we are born debtors.

Then, to make the obligation about the social debt compatible with individual liberty, Léon Bourgeois uses a contractual conception of obligation (Blais 2007 : 35). He employs what he calls a quasi-contract, a purely voluntary act that results in a commitment of the person who benefits from it without being entitled to it. When parents take care of their children, this is a voluntary act. According to a quasi-contract viewpoint, their child is committed to this caring act, even if they did not ask for this care and even if their parents do not have a specific return right (a kind of reimbursement for their care). Because the child benefits from something necessary for them, the quasi-contract commits them. Hence, the quasi-contract justifies an obligation retroactively granted without agreement.

This justification of solidarity seems to directly conflict with certain core principles of liberalism, like some conceptions of liberty and ontological individualism. Bayertz mentions this hypothesis (1999 : 4) in the following way:

One of the reasons behind this theoretical neglect is the fact that positive obligations to act, as the term solidarity implies, are difficult to incorporate within mainstream ethical and political thought. Modern Age ethics and political philosophy have a fundamentally defensive orientation: they aim primarily to ward off dangers to the individual accruing from competition with other individuals, the maelstrom of social conformity, or the powers of the State.

I will begin by discussing the constraining feature to show how it conflicts with two conceptions of individual liberty, which are central to many liberal approaches. I will not focus on ontological individualism, although I will briefly elaborate on it when I address the question of autonomy.

Liberalism and liberties

Liberalism is not a family of thought with fixed boundaries. Significant differences exist between thinkers typically identified as liberals. Sometimes connections are not robust but are more accurately characterized by what Wittgenstein calls "family resemblance" (2009 [1953]).

Nevertheless, a useful distinction can be made by identifying two ways of addressing liberalism: as a comprehensive ethic or as a political ideology. In this work, I focus solely on the aspect of political ideology. I aim to advocate for a specific form of political solidarity, occasionally referred to as civil solidarity (Alexander 2014 : 307; Supiot 2015 : 16), which seeks to establish a more expansive sphere of mutual assistance than the solidarity spaces commonly identified in sociology (family, friends, tribe, etc.). How does this political solidarity relate to a political ideology where individual liberty occupies such a significant space, as in liberalism? To answer this question, we must determine which aspects of liberalism will likely conflict with solidarity.

Political liberalism maintains that it is possible to conceive the most minimal moral foundation to ensure peaceful political association (Larmore 1996 : 123). Authors refer to this moral foundation as axiological neutrality. Collective institutions must strive to gain the support of individuals, regardless of their personal conception of the good (Gaus : 2004).

Catherine Audard proposes identifying a certain number of concepts inherent to liberalism, the most central of which would be valuing individual liberty based on the idea that

there is no natural subordination of human beings. Each individual is sovereign and free to decide for himself in the face of all authorities, moral or religious, powers, political or otherwise, all despotisms that would like to submit him[8]

Audard 2009 : 29

The centrality of individual sovereignty originates from an individuated ontology of the human, which posits that human beings are individually unique and indivisible. Humans can realize themselves as individuals, primarily through their reflective and rational capacities (Audard 2009 : 30).

Almost all liberal authors share this emphasis on individual liberty, whether they are perfectionists or pluralists, explicitly democratic or not, and irrespective of their conception of law. Some authors refer to this focus on individual liberty as the Fundamental Liberal Principle (Gaus 1996 : 162–166) to underscore that the burden of justification lies with those who would curtail natural human liberty. This centrality is evident in the Rawlsian conception of justice[9]. In contrast, solidaristes do not prioritize individual liberty to the same extent. While they value individual liberty, they balance it with solidarity. Therefore, we examine this specific aspect of liberalism to comprehend why the solidarist approach creates tensions from a liberal perspective.

Individual liberty as negative liberty

There are at least two popular ways of defining individual liberty within liberal thought. We can first define it as negative. Isaiah Berlin conceptualized it in 1958 as a space of non-interference within which the individual can move without constraint.

Liberty in the negative sense involves an answer to the question: 'What is the area within which the subject—a person or group of persons—is or should be left to do or be what he is able to do or be, without interference by other persons

Berlin 1969 : 121

As with most public policies, the organization of solidarity by the State often interferes with negative liberty. Indeed, all values, not just solidarity, may conflict with it. Although liberals like Berlin are concerned about such interference, they acknowledge that certain constraints are necessary for fostering harmonious coexistence. In contrast, Rawls contends that liberty's only acceptable limitation is to protect it. He aims to maximize its value, even if that entails compromising it in the process (Rawls 2009 : 5). Consequently, when understanding liberty as negative liberty, several issues arise:

Claims made of the individual are principally met with mistrust; when it comes to obligations, increased pressure is exerted to ensure that they are justified. With this in mind, manifestations of solidarity may be morally commendable, but they cannot be made binding.

Bayertz 1999 : 4

From this, it becomes difficult to avoid significant interference when developing mutual assistance requirements. For instance, having a child can be wonderful when we have consented to it. However, the child creates multiple infringements on negative liberty: the parents must support the child at all hours of the day and night. Negotiating or planning certain activities inherent in the child's development becomes impossible.

This criticism could be qualified: we create a new moral agent when we have a child. As a result, the child's negative liberty bubble reduces our non-interference space. This bubble is not solely a space of negative liberty since the child depends on adults for survival and growth. Thus, parents intervene in this bubble and anticipate the child's needs without obtaining free and informed consent. We could argue that the child has not developed enough to enjoy individual liberty. Consequently, the child's liberty differs from negative liberty due to vulnerability and reliance on adults.

This example illustrates how welfare-state policies conflict with negative liberty. Some welfare-state measures provide crucial support to vulnerable individuals — for example, minimum social benefits and housing. This infringes upon negative liberty, just as parental care does. However, as demonstrated in the child example, without these welfare policies, people cannot enjoy individual liberty anyway due to extreme helplessness. Therefore, we should question whether such policies can violate negative liberty when such liberty seems absent.

An important distinction exists with the child example. Welfare-state policies do not result from arbitrary parental choices but from a collective decision-making process.

There is a connection between nationalism and liberalism, positioning individual liberty as a fundamental principle within a nation-state framework (Tamir 1993 : 139). Historically, nationalism has justified solidarity policies compatible with liberalism (Kymlicka 2015 : 2). The Beveridge report exemplifies how British politics advocated for a welfare state with a liberal approach (Whiteside 2014 : 3). Politicians have employed the previous child metaphor, which continues to be used to describe how the welfare state influences citizens' liberty[10].

The nationalist justification for constraints on individuals posits that restricting liberty is acceptable when it occurs within a specific political community governing itself. This understanding of individual liberty deviates from negative liberty. To David Miller, "Nations are communities whose members see themselves as having obligations of mutual aid that are more extensive than the aid they owe human beings generally" (Miller 2007, 131). This concept of national solidarity – particularlydeveloped by liberals like John Stuart Mill and Henry Sidgwick – assumes that feelings of attachment to a community or nation are necessary for social cohesion. The stronger the cohesion, the less constraining the constraint. It does not conflict with individual liberty but merely expresses the aggregation of individual wills for the common interest (Freeden 2008, 152).

This limitation of solidarity by national borders – though not necessarily by the State – played a historically significant role in expanding and justifying solidarity in Western Europe in the 19th century. Furthermore, this justification does not directly clash with individual liberty. Several liberal authors also support the nation-state and nationalism[11]. However, such a nationalist limitation seems neither desirable in an era of questioning the Westphalian nation-state model (Fraser 2010) nor necessary to justify solidarity (Banting and Kymlicka 2017; Kymlicka 2015). Even for some liberal authors, nationalism today becomes untenable when confronted with broader ethical demands (Hayter 2004; Jones 2019) or when faced with liberal multicultural situations.

In short, while liberal democracy has benefitted in important ways from its link with nationhood, minorities have often paid a high price. They have been faced with social stigmatization and racialization, at best offered a stark choice of assimilation or exclusion, and at worst subject to expulsion or genocide [12].

Banting et Kymlicka 2017 : 19

To prevent minorities from bearing a high cost, some authors suggest that nationalism can be refined – reducing its attachment to a specific conception of the good, as described by Michael Walzer (2004) – while maintaining its cohesive power (Miller 1995; Rorty 1998; Tamir 1993) for individuals who might otherwise be marginalized due to economic, racial, or gender inequalities. This refinement should enable the nation to become more inclusive without sacrificing its motivational effectiveness in fostering shared solidarity. According to these authors, a sense of belonging – such as that experienced by an intergenerational group with a shared history within a territory – is necessary to ensure political stability and solidarity.

Will Kymlicka and Keith Banting likely advocate the most minimal version of this approach. These two authors envision nationalism with two safeguards to protect minorities: implementing multicultural recognition policies and excluding pre-political components from the conditions of integration within the solidarity group (Banting and Kymlicka 2017 : 20). However, Banting and Kymlicka base this refined version of nationalism on a conception of individual liberty, not as negative liberty but as autonomy. We will now examine the extent to which liberty as autonomy is more or less compatible with the concept of solidarity.

Liberty as autonomy and ethical justification

Autonomy is how many liberal authors like Will Kymlicka and Joseph Raz conceive individual liberty. Their concept differs from the Kantian one, "according to which individual liberty should be equated with morality as a whole, understood as consisting of self-determined principles; in this case, autonomy is meant to refer to the liberty of individuals to choose their own lives" (Blattberg 2011 : 124). I will focus on autonomy, as understood by Raz and Kymlicka.

This conception is interesting in the context of solidarity because it is the most likely to accommodate constraint. Autonomy involves critically reflecting on the reasons one has for accepting a specific belief or undertaking a particular course of action. Autonomy requires "appropriate mental abilities, an adequate range of options, and independence" (Raz 1986 : 372). Sometimes, restricting liberty (understood negatively) to promote autonomy is acceptable, even necessary (Digeser 1995 : 177). For example, students must remain in class (their liberty, understood negatively, is limited) because we believe school helps them become autonomous individuals.

Let us consider why autonomy appears to be a suitable candidate for justifying the constraint of solidarity. If we view solidarity as aiming to enhance autonomy by combating social phenomena that reduce it – such as poverty, racism, and sexism – the welfare state constraint seems more acceptable to proponents of this form of liberty. In a capitalist society, impoverished individuals have fewer options than wealthier ones. These options are even more limited for a poor, racialized woman in a racist and sexist society.

However, a crucial aspect of this conceptualization conflicts with solidarity. Liberal autonomy necessitates the presence of choices to achieve it. Since solidarity entails a normatively shaped, complex interdependence, it does not always provide multiple options. Occasionally, solidarity requires long-standing policies and extensive collective involvement to be efficient or consistent with the common good it deserves. Nevertheless, people do not always consent to or choose this involvement. Every time you pay your taxes, you are unaware of who will benefit and how your money will be utilized.

Therefore, we should accept a reduced scope for solidarity's actions to prioritize autonomy. This prioritizing provides good reasons to believe that only specific kinds of solidarity, such as optional solidarity, would be operationalized due to its lesser constraint on choices. Private insurance systems exemplify this consideration when they are optional. Can we find a way to preserve autonomy without compromising a more radical conceptualization of solidarity, which implies a greater degree of constraint?

In addition to the positivist justification mentioned earlier with Bourgeois and the liberal nationalist justification, there exists a third type of justification for the constraint necessary for solidarity. Some authors support this ethical justification by proposing that solidarity be conceived as a universal value. Authors then define solidarity as an anti-consequentialist principle that unites a group with each individual who composes it (Foot 2002; Wiggins 2009). Solidarity thus becomes a safeguard against the sacrifice of minorities, even if such sacrifice benefits the group.

The advantage of this justification is that it enables solidarity to be compatible with the ethical foundations of contemporary liberalism. Consequently, we practice solidarity not with something but against abandonment. This conception allows solidarity to become a universal value by including everyone (eschewing partiality)[13]. Solidarity no longer requires borders and opposes individual sacrifice, regardless of which group mandates it. This universalist solidarity emphasizes that the "we" depends on each individual comprising it. This approach makes solidarity compatible with a universalist reading of liberalism, that is, cosmopolitanism.

However, this justification of solidarity can be misleading. There is not a rights-based duty to protect autonomy; hence solidarity's constraint should be seen as demanding for some liberals, as Joseph Raz (2009 : 247) says:

A right to autonomy can be had only if the interest of the right-holder justified holding members of the society at large to be duty-bound to him to provide him with the social environment necessary to give him a chance to have an autonomous life. Assuming that the interest of one person cannot justify holding so many to be subject to potentially burdensome duties, regarding such fundamental aspects of their lives, it follows that there is no right to personal autonomy

Raz does not regard the denial of an autonomous life by social institutions or social hierarchy as a violation of a fundamental right to autonomy. Raz believes we should not force people to provide all the collective goods necessary for autonomy[14]. Thus, autonomy may not be the best option if we aim to legitimize the constraining dimension of solidarity, considering that solidarity should emancipate individuals from social hierarchies.

Therefore, the constraint is essential for the concrete realization of solidarity (Cureton 2012 : 692-93). However, even for proponents of solidarity, this constraint must not be detached from adherence, from its justification as legitimate (Laborde 2015 : 122). How can we consider this adherence from a philosophical perspective? In other words, can we find a better conceptualization of liberty suitable for solidarity, meaning it preserves all the criteria mentioned above of solidarity?

Suppose we accept that the tension generated by the demand for individual liberty – understood as autonomy or negative liberty – undermines collective constraining solidarity, i.e., suppose there is a (potential) conflict. What criterion can we use to protect individual liberty? In the following section, I take a step back to explore a political conception of political liberty that allows for initial non-consent without sacrificing individual liberty.

Refunding Solidarity on a new justification of Constraint

There is no question of proposing a new theory of solidarity; instead, the aim is to offer a direction for future studies that seek to explore this reconfiguration systematically. From a neo-republican perspective, such a configuration is sustainable if we accept that non-domination is a common good we must pursue through solidarity. To explain this, we must first take a brief historical detour to examine the context of solidarity's emergence in Europe.

It may seem odd to posit an opposition between liberalism and solidarity. Some contemporary authors view solidarity as a means of reforming liberalism to make it more viable and enable it to withstand ideological competition from socialism in the 19th century[15]. These authors regard welfare states as the most effective tools of liberal ideology for preserving an unequal capitalist economy. According to them, the welfare state is not a means of resisting liberalism but rather a tool for legitimizing it (Crouch 2017; Pierson 2002).

I challenge two assertions that associate liberalism and solidarity. First, although we can see the welfare state as an embodiment of solidarity, it is not the only political form of solidarity. It is also possible to view certain minimal welfare states, such as the liberal form described by Gøsta Esping-Andersen (2007), as being closer to Christian charity than to the notion of reciprocity championed by republican solidarity[16].

Second, even if solidarity emerged during a period of liberalism's decline in the face of socialism, and thus as a means of reforming liberalism, it can still be considered a more radical idea than it appears. The new social challenges of the second half of the 19th century, brought about by successive European industrial revolutions, undermined liberal ideals. Consequently, liberalism could no longer defend individual liberty without considering the economic and social context and had to acknowledge that obstacles to liberty were no longer found solely in state interference or others but also indirectly through social conditions themselves (Audard 2009 : 269). Liberalism thus seemed to intersect with solidarity by developing the concept of welfare, which would later give rise to the welfare state (Blais 2007 : 259-260).

In France during the same period, the concept of solidarity emerged as a persuasive political ideal for the defenders of the Third French Republic. They sought to develop a secular social doctrine—distinct from Christian charity—that could address the challenges of liberal industrialization. The solidaristes framed solidarity as a republican third way, situated between liberal individualism and collectivist socialism (Blais 2007 : 13).

It is intriguing to reconsider the neo-republican perspective in order to find a justification for coercion that respects both the concept of solidarity—as a departure from liberal individualism—and individual liberty. One way to justify the coercion necessary to achieve solidarity within a republican framework is to reconfigure the relationship between solidarity and liberty. Liberty should no longer be considered as a separate or even opposed element to solidarity but rather as an integral part of it. The goal should not be to achieve solidarity at the expense of liberty but to preserve and enhance it. Solidarity is no longer defined merely as a principle for combating poverty or economic inequalities but as having a broader instrumental purpose: realizing liberty as a common good.

To ensure the coherence of this reconfiguration, it is also necessary to reevaluate the conception of liberty. Envisioning liberty as non-interference or autonomy while avoiding atomistic individualism within a concept based on a non-atomistic social ontology (as opposed to the views of Berlin, Kymlicka, or Raz) may help resolve potential tensions. We must therefore turn to a conception of liberty compatible with an anti-atomist social ontology to use the expression of Philip Pettit (2004 : 7), that is to say, which takes for granted that

individuals depend either constitutively or non-causally on their relationships with others for the possession of a particularly important human capacity e.g., […] being able to reason and think individually[17].

As previously mentioned, solidarity assumes interdependence among humans. In other words, no one can realize their potential in isolation, detached from the human network in which they are born, developed, and functioned. The individualistic aspect of classical liberalism endorses a different conception, where individuality takes precedence and exists prior to the entanglement of individuals in society.

In contrast, the political use of solidarity offers an entirely different approach: human interdependence is inevitable, and we must shape it according to shared principles. Individual liberty does not preexist life in society; instead, it is the community that enables the realization of a specific form of liberty: liberty as non-domination.

This form of liberty is not defined as the absence of obstacles or interference but as the absence of vulnerability to intentional and arbitrary interference by a third party. The arbitrary nature of interference is determined by the extent and nature of the involvement of those subjected to it in creating the constraint. In other words, the more a rule results from a democratic and inclusive process, the less likely it is to be interpreted as domination. This principle can also apply to two individuals, meaning each respects the other's liberty as non-domination. Thus, the question arises: why to invoke democracy? Solidarity helps preserve liberty, understood as the absence of domination, by reducing dependencies on arbitrary constraints linked to the market economy and oppressive systems such as racism (Hooker 2009; Quadagno 1994; Shelby 2005). However, it is crucial to demonstrate how solidarity reduces arbitrary constraints arising from the market and mitigates racism.

Participation in policies implementing solidarity to guarantee the non-domination of each member against, for example, the capitalist market economy[18], can be made compulsory because it is seen as a repayment of the social debt described by Léon Bourgeois and the full realization of a non-atomistic social ontology.

Viewing solidarity as the realization of a common good, understood as non-domination, allows us to reconnect with the republican tradition that significantly influenced the creation of the concept in the 19th century. Consequently, the realm of solidarity is not primarily that of individuals who are also individually free but rather that of individuals who are equally non-subjugated, as articulated by Nancy Fraser (2010). In this configuration, "justice-triggering political relations exist whenever a collection of people are jointly subjected to a governance structure that sets the ground rules governing their interaction" (Fraser 2010 : 293).

Conclusion

Despite its significant media presence, particularly during the COVID-19 pandemic, the notion of solidarity remains somehow neglected in contemporary political science (Alexander 2014; Bayertz 1999). As I have shown, philosophers and intellectuals in the 19th century indeed used the idea of solidarity, in particular during the French solidarist movement (Léon Bourgeois, Alfred Fouillée, Charles Secrétan) and alongside the development of sociology as an autonomous discipline (Émile Durkheim, Auguste Comte). While today the field of political philosophy would seem the most likely discipline to discuss and study solidarity, it continues leaving this moral concept out of its theoretical considerations.

All of this led me to answer the central question: why is it so tricky to comprehend solidarity as a political ideal? I argue that this is due mainly to the prominent role of liberalism in political philosophy and the perception that solidarity is incompatible with liberalism's primary value, that of individual liberty. Furthermore, solidarity generates tension with its particularistic and constraining dimensions, both at the core of the concept. Solidarity establishes a division between "us" and "them," thereby supporting diverging attitudes towards insiders and outsiders of a given group.

Not only does the particularistic dimension of solidarity conflict with the universalist morality dear to many liberalists, but solidarity's constraining dimension also conflicts with individual liberty. This is why, to analyze the various tensions within the notion of solidarity, I also discussed negative liberty (Berlin 1969) and liberty as autonomy (Kymlicka 2015; Raz 2009). While solidarity collides with negative liberty to the extent that it constrains individuals, autonomy seems to be a more suitable version of liberal liberty because it allows for constraint. However, autonomy provokes tensions with the particularistic dimension of solidarity by evacuating constraint shaped by the good life. That is why liberty as non-domination emerges as the most helpful approach for an influential conceptualization of solidarity, which does not conflict with individual liberty.

As we continue to grapple with the complexities of solidarity in political philosophy, another captivating avenue to explore is the potential role of solidarity in addressing the urgent challenges posed by climate change. Climate change, as a global issue, demands international cooperation and shared responsibility among nations, communities, and individuals. Solidarity may provide a vital ethical framework to guide the development of policies and strategies that prioritize the collective good and safeguard the planet's most vulnerable populations. By reexamining the connections between solidarity and non-domination in the context of climate change, we could foster a more unified and effective approach. Consequently, delving into solidarity's potential contributions to climate change discourse could not only reinvigorate its standing within political philosophy but also catalyze innovative solutions for one of humanity's most pressing concerns.