1. Solidarity in the Western Tradition: Shifting conceptualizations

Much of the literature on solidarity in the Euro-American tradition usually refers to the Latin expression obligatio in solidum as the starting point of normative thinking about solidarity.Footnote ⁹ This expression, which dates back to the works of Roman jurists like Gaius, and can be found in Justinian’s Digest (Digest 45.2, 46. 1), offers a window for understanding our modern-day use of the term solidarity. The Roman term is a composite of two words (obligatio and solidum) joined together by the preposition in. Obligatio, for its part, can be further unpacked into two words, ob (“on account of,” “because of,” “for the sake of”) and ligo (to tie, bind). This means that when we have an obligation to do something, we tie ourselves to do that thing.Footnote ¹⁰ Solidum, on the other hand, which appears here in the accusative, following the preposition in, is a declension of solidus, which means “whole,” “complete.” The connotations of the word also include meanings like “to make firm, dense, or solid.” The expression is found in the Roman law of obligations where, when multiple debtors were bound to a creditor for a single contract, each individual debtor could be held accountable for the entire sum. For example, if A, B, and C borrowed money together in solidum and B and C defaulted, the creditor could sue A for the full amount. If A paid, the debt was gone, and A had to seek repayment from B and C internally. The reasoning behind this type of arrangement could be attributed to the fact that entering into a loan agreement in solidum implies that the debtors were tying themselves (obligatio) into a solidum to benefit from the loan as a whole.

Solidarity was not invoked much during the Christian medieval period, where theologically-informed notions like charity and religious fraternity, as well as forgiveness, were the mainstay. It was not until the nineteenth century, particularly in France, that solidarity began to feature again strongly. This reappearance is closely linked to the profound social and political transformations associated with industrialization, urbanization, and the aftermath of the Revolution, all of which contributed to the erosion of traditional forms of social cohesion and the intensification of class conflict.Footnote ¹¹ In this context, solidarity emerged as a key analytical and normative concept through which French thinkers sought to theorize new foundations of social integration compatible with republican institutions.Footnote ¹²

Early contributions can be identified in Auguste Comte’s emphasis on moral consensus and social order, as well as in Frédéric Le Play’s empirical analyses of social organization through family and labour structures. The concept reaches its most systematic sociological formulation in Émile Durkheim, who distinguishes between mechanical and organic forms of solidarity as corresponding to different stages of social differentiation. Solidarity acquires its most explicit political articulation in Léon Bourgeois’ Solidarité. In his view, individuals benefit from an inherited stock of social goods such as institutions, knowledge, and infrastructure, to which they have not proportionally contributed; thus, they incur what he terms a “social debt” (dette sociale). This obligation is not grounded in explicit consent, but is instead conceptualized through the idea of a “quasi-contract,” whereby participation in social life itself generates duties analogous to those of obligatio in solidum. In effect, what Bourgeois does is to transform the Roman legal principle into a moral and political doctrine. Solidarity, on this account, becomes a justificatory principle for redistributive justice: it legitimizes mechanisms such as taxation and social welfare as means through which individuals discharge their diffused but binding obligations to the collective.Footnote ¹³

It is in this body of work that we begin to see how two accounts of solidarity seem interwoven and sometimes in tension with each other. On the one hand, nineteenth-century French thinkers mobilize solidarity as a response to the crises of modernity: industrial inequality, social fragmentation, and the erosion of traditional hierarchies. Yet they do not treat it as something that can be generated without underlying conditions of societal integration. Rather, they seem to suggest that solidarity presupposes a prior or emergent form of bondedness that renders social obligations meaningful (deep solidarity). For Comte, for example, this takes the form of a shared moral consensus underpinning social order; for Durkheim, solidarity, even in its “organic” form, depends on a residual collective conscience capable of regulating differentiated roles; and for Bourgeois, the doctrine of social debt presumes the recognition of a factual condition of interdependence that binds individuals into a quasi-contractual community.Footnote ¹⁴ Thus, while invoking solidarity as a remedy to injustice, they simultaneously rely on a substrate of social cohesion without which the very idea of mutual obligation would lack force.

The concept of solidarity underwent further transformation over the course of the twentieth century, shifting from a primarily sociological and moral framework to an explicitly political and mobilizing one. This orientation shifted with the intensification of industrial capitalism and the emergence of mass labour politics in the early twentieth century. Within Marxist theory and trade union practice, solidarity came to denote collective alignment in the face of exploitation and was reframed as a precondition for effective class struggle.Footnote ¹⁵ The experience of global wars and ideological polarization further expanded its meaning: solidarity became intertwined with nationalist mobilization, anti-fascist resistance, and internationalist commitments that transcended state boundaries.Footnote ¹⁶ By mid-century, decolonization struggles in Africa and Asia rearticulated solidarity as a global political principle, linking geographically-dispersed actors through a shared opposition to imperial domination and racialized hierarchies.Footnote ¹⁷

In the latter half of the century, solidarity was further reconfigured through civil rights, feminist, and other identity-based movements, which foregrounded structural injustice and the politics of recognition. Here, solidarity entailed not only shared material interests but also forms of affiliation across differences, often grounded in lived experience and normative commitments to equality.Footnote ¹⁸ This reconceptualization also generated sustained theoretical reflection on the conditions and limits of solidarity in pluralistic societies, as seen in the works of Habermas and Scholz, who distinguish between civic, social, and political forms of solidarity.Footnote ¹⁹ By the late twentieth century, solidarity had become emblematic of collective political agency directed against authoritarian and systemic forms of power, consolidating its status as a central concept in the vocabulary of modern resistance. This was exemplified in movements like Solidarnosc in Poland and anti-apartheid alliances across different world regions.

However, not everyone was comfortable with the invocations of solidarity in public life. Within liberal and libertarian frameworks, solidarity is often treated with suspicion insofar as it appears to justify coercive obligations in the name of collective welfare. Thinkers such as Friedrich Hayek and Robert Nozick argued that solidaristic claims can obscure infringements on individual liberty, especially when mobilized to defend redistributive policies or state intervention.Footnote ²⁰ In public health, this critique is echoed in the resistance to measures such as mandatory vaccination, quarantine, or universal health financing, where appeals to solidarity are viewed as threatening individual autonomy and consent.Footnote ²¹

A distinct line of critique emerges in conservative and communitarian perspectives, which do not reject solidarity outright but contest its abstraction and politicization. Conservative thinkers tend to defend solidaristic obligations rooted in historically embedded communities such as family, nation, or religious institutions, while expressing scepticism towards universalistic or cosmopolitan formulations that detach solidarity from these concrete social forms.Footnote ²² Communitarian theorists likewise caution that modern, state-mediated invocations of solidarity may become thin and bureaucratic, displacing the moral density of face-to-face communal relations.Footnote ²³

Within critical, feminist, and postcolonial traditions, resistance to solidarity takes a more reflexive form, focusing on the internal tensions and exclusions that solidaristic discourse may generate. Scholars such as Chantal Mouffe and Judith Butler argue that solidarity, when premised on assumptions of unity or shared identity, can suppress difference and marginalize dissent within political movements.Footnote ²⁴ Postcolonial critiques extend this concern to the global arena, where invocations of solidarity in development and health can reproduce paternalistic relationships between the Global North and South.Footnote ²⁵

Looking at global health, these tensions and ambiguities were particularly evident during the COVID-19 pandemic. Despite widespread rhetorical commitments to “global solidarity,” practices such as vaccine nationalism and the protection of intellectual property regimes limited equitable access, revealing the gap between normative aspiration and geopolitical reality.Footnote ²⁶ Recent debates within public and global health ethics further underscore the contested status of solidarity as both a guiding ideal and a practical principle.Footnote ²⁷ Some scholars defend solidarity as a necessary corrective to the individualism of mainstream bioethics, emphasizing interdependence, shared vulnerability, and reciprocal obligation in the governance of health systems.Footnote ²⁸ Others, however, caution that solidarity remains normatively indeterminate and susceptible to political instrumentalization, lacking clear criteria for distribution and enforcement.Footnote ²⁹ Consequently, in areas such as universal health coverage, priority-setting, and pandemic response, solidarity operates as a site of ongoing contestation, mediating tensions between autonomy and obligation, local attachment and global responsibility, and ethical commitment and institutional feasibility.

Taken together, this historical excursus reveals that solidarity has undergone a series of conceptual expansions and displacements. It has shifted from a juridical principle of shared liability (obligatio in solidum), to a sociological account of social cohesion, to a normative doctrine of redistributive justice, and finally to a politicized and contested principle of collective action and resistance. Each transformation widened the scope of the concept. And, as Aristotle rightly points out, the relationship between the scope of a concept (its extension) and its precision (its definition) is inverse: the wider a concept is, the less defined it is. As solidarity moves from bounded, contractual relations, to diffuse, global, and often asymmetrical contexts, it generates persistent tensions: between coercion and voluntariness, between embedded and abstract forms of belonging, and between unity and difference. The contemporary challenge, therefore, is not simply to affirm solidarity as a moral or political ideal, especially in the international domain, where not all parties are a product of the Western philosophical and cultural traditions, but to specify its grounds, limits, and modes of institutionalization in inclusive ways that can reconcile its expanding scope and differentiated conceptualizations.

2. Deep and responsive solidarity

The conceptual shifts identified in Section 2 are articulated within the Euro-American philosophical tradition, which reflects a particular set of ontological assumptions and historical experiences. African and Asian philosophical traditions, for example, generate accounts of solidarity that place emphasis on other aspects of the concept. If epistemic justice is accepted as a normative requirement, then privileging a single intellectual tradition is unjustified, especially in the formulation of international agreements intended to bind plural constituencies. A more adequate account of solidarity must incorporate perspectives beyond the Euro-American canon. The next section advances this claim by examining solidarity within African philosophical traditions.

To ground this analysis, we reflected on key themes of solidarity in the African philosophical literature. Drawing from analyses of “solidarity,” “ubuntu,” and cognate concepts such as umunthu, hunhu/unhu, botho, sotho, seSotho, seTswana, ujamaa, harambee, fihavanana, omoluabi, eniyan, and igwebuike, we noted the following findings which underpin our reflections on deep and responsive solidarity in this paper:

Within African philosophy, solidarity is considered as a constitutive element of communitarian moral frameworks.Footnote ³⁰ In particular, ubuntu and related traditions treat communal relations as the primary locus of moral value, with solidarity functioning as a core norm that underwrites social harmony and collective flourishing.Footnote ³¹ Given its consistent association with communitarian thought, solidarity is not a peripheral virtue; rather, it is integral to the structure of moral reasoning within these frameworks.Footnote ³²

Within this tradition, solidarity requires agents to participate in cooperative practices that are oriented towards shared ends, and to subordinate narrow self-interests to the flourishing of others. Some accounts go further to add that rights are secondary to duties.Footnote ³³ Importantly, solidarity is not reducible to affective states such as compassion or sympathy. Instead, it denotes a stable, action-guiding commitment to the communal good, realized through choices and practices that are reasonably expected to benefit others.Footnote ³⁴ Such practices are typically grounded in a form of identification in which others are regarded as “another self,” such that their flourishing partly constitutes one’s own.Footnote ³⁵

Some accounts restrict solidarity to relations within bounded communities, while others extend it to all persons on the basis of shared humanity—Wiredu’s onipa na ohia (it is the human being that matters) embodies this view.Footnote ³⁶ On the latter view, if moral obligations arise from ontological relationality rather than from contingent group membership, then there is no principled basis for limiting solidarity to in-group relations. Instead, solidarity generates generalizable obligations to promote the well-being of others, thereby repudiating excessive parochialism and competitive individualism.Footnote ³⁷

This position is grounded in a relational moral ontology of personhood. Theories of personhood in the African tradition distinguish between a descriptive account grounded in intrinsic capacities such as spirit and soul -sunsum, okra or in the capacity for social participation, and a normative account in which personhood is achieved through the enactment of pro-social communal virtues.Footnote ³⁸ On the normative account, virtues such as care, compassion, and solidarity are constitutive of personhood.Footnote ³⁹ Failure to act in solidarity is, in a morally significant sense, to fall short of full personhood. In this respect, solidarity is both constitutive of moral agency and prescriptive of moral obligation.Footnote ⁴⁰ Thus, moral evaluation is relational: actions are right insofar as they promote harmonious relationships and sustain communal bonds.Footnote ⁴¹

Solidarity is not merely theorized; instead, it is institutionalized as a pervasive feature of social life. In many African contexts, solidaristic norms are so embedded in everyday practices that they function as default expectations rather than exceptional moral demands.Footnote ⁴² Examples of such practices include nnobua (a mutual-help cooperative among farmers), contributions to assist others in difficulties (like bereavement or illness), or celebrating their successes (like weddings and the arrival of a newborn). Taken together, these considerations support the claim that solidarity is a necessary condition for the persistence of communal life. Without solidaristic practices, the structures on which communities depend would erode, undermining their capacity for collective survival and flourishing.Footnote ⁴³ This explains why solidarity is ultimately oriented towards collective well-being, understood as “faring well together.”Footnote ⁴⁴

African thinkers are also keenly aware that this relational framework can generate tensions. When communitarian theories accord ontological primacy to the community, the individual’s well-being may be subordinated to collective interests.Footnote ⁴⁵ African feminist authors have also highlighted that this form of oppression can potentially occur, not only towards individuals, but also towards particular groups within a community. Gyekye advances the idea of moderate communitarianism, where the individual’s well-being (all individuals) becomes the central focus of community as an antidote to what he describes as “radical communitarianism” which had been proposed by authors like Menkiti.Footnote ⁴⁶

Within this debate, solidarity emerges as a commitment to identifying and correcting inequities embedded within the relational web. Because solidarity requires and is grounded in identifying with the humanity of others, its aim is not merely to sustain communal bonds for the sake of community, but to ensure that the bonds within which people emerge and live are equitable enough to enable all to flourish. This includes addressing structural and embedded historical inequalities and recalibrating communal practices to better align with the well-being of all.Footnote ⁴⁷ In this way, solidarity both affirms relational interdependence and subjects it to normative scrutiny, thereby providing a principled basis for addressing injustice within as well as across communities.

It is possible, here, to distinguish between two analytically distinct forms of solidarity, which we term Deep and Responsive solidarity. Deep solidarity is grounded in a relational ontology of being according to which persons are conceived of, not as independent entities who subsequently enter into relationships, but are instead constituted by relationships that precede and sustain them.Footnote ⁴⁸

From the bedrock of Deep solidarity, another type of solidarity which we call Responsive solidarity emerges. Responsive solidarity, as distinct from Deep solidarity which characterises the ordinary normal way of life, arises when individuals or groups come together to support others to overcome challenges in times of adversity or common threats. This type of solidarity is reactionary, rallied and enacted as a response to unfavourable conditions or situations, or to a perceived or real threat. The threats can be “natural” unfavourable events such as floods, famine, earthquakes, disease and death; but they can also be specific political, social or cultural injustices, such as forms of discrimination or oppression based on gender, ethnicity, religion, social class, or disability, among others.

Responsive solidarity is motivated and directed towards specific, clear, fixed, executive goals that are often attainable, to improve or correct disadvantage or injustice, either present or past, or to deal with common threats.Footnote ⁴⁹ For instance, solidarity among the Shona was driven mainly by a collective insecurity from potential foreign attacks.Footnote ⁵⁰ Therefore, their practices of solidarity manifested predominantly in cooperative ways to either prevent or overcome their common existential threat.

Responsive solidarity is usually transient, depending on the nature of the adversity it seeks to address. Also, responsive solidarity often has a targeted adversary, since it involves standing together with others against a common enemy or threat. Chimakonam describes it as a negative form of solidarity, as it reflects the tendency to work together and cooperate only when there is a common threat to fight or overcome.Footnote ⁵¹ This makes Responsive solidarity adversarial, where individuals and/or groups stand against a targeted adversary or enemy, which could be persons or situations.

Responsive solidarity is similar to what the 2023 revised Draft on Human Rights and International Solidarity describes as reactive solidarity, which is characterized by collective or individual actions to respond to and solve global challenges. In a global context, Responsive solidarity can be triggered by and targeted at solving health emergencies, environmental degradation, climate change, armed conflict, forced migration, trafficking of persons, poverty, including extreme poverty, food insecurity, all forms of violence against women and children, racism and discrimination, violent extremism, terrorism, colonialism, and foreign invasions.

3. Solidarity in global health

What we see from the foregoing analysis are two different but related ways of thinking about solidarity. On the one hand, we have seen the shifting conceptualization of solidarity in the Euro-American tradition from a legal concept to a broader, more political view, where individuals stand together to fight against conditions they perceive as unjust. This way of coming together is commonly perceived as voluntary and corresponds more to what we have described as Responsive solidarity because it is a reactive response to unfair conditions. While we admit that the categories “Western” and “African” are not mutually exclusive in terms of their analyses of solidarity, they nevertheless exhibit some distinct patterns which make it possible to classify them as such. For instance, notions such as relationships, unity, similarities, and interdependence feature in analyses of solidarity in both traditions.Footnote ⁵² However, the African tradition places greater emphasis on deep solidarity grounded in relational ontologies that consider solidarity as the ordinary moral way of living in and organising societies. The Euro-American tradition, we could say, without necessarily omitting deep solidarity, often takes it for granted in the pursuit of responsive solidarity goals. In the African view, solidarity is seen as part of the moral life of persons and institutions; therefore, solidarity in times of emergencies (Responsive solidarity) is only a continuation and harnessing of existing commitments grounded in Deep solidarity.

When we look at global health from these two traditions of conceptualizing solidarity, a conundrum emerges. For those who rely solely on the Euro-American tradition to promote solidarity in global health, the concept becomes one of responding to the inequities that continue to permeate the global health space. These inequities range from access to healthcare to epistemic justice and extractivism and colonialism, among others. Solidarity from this viewpoint becomes a locus of activism that seeks to address these injustices by rallying voices to decry and combat the drivers of inequity, more particularly, the actors and nations who are perceived as drivers. It is characterised by some degree of adversarialism, as responsive solidarity often is, because it seeks to challenge, denounce, and change the structures and institutions that are perceived as driving, perpetuating, or enabling the current status quo of inequity in global health.

In fairness, this view is not wrong. The failures of the COVAX initiative during the Covid-19 pandemic were a stark example of how rich countries, whilst appealing rhetorically to solidarity, continued to perpetuate health inequities by hoarding vaccines or dumping near-expiring vaccines on poor countries.Footnote ⁵³ The hesitation to agree to share resources with poor countries, particularly patents and licenses for producing pandemic-related health products locally, was reflective of the refusal to commit seriously to solidarity with “other” peoples and countries, thereby reinforcing the sometimes-exclusionary character of solidarity. The same could be said about the ongoing impasse in the negotiations of the Pathogen Access and Benefit Sharing (PABS) agreements of the Pandemic Agreement at the World Health Organization, where countries, mostly from the high-income bracket, are deeply uncomfortable with the idea of sharing the health products that accrue from research on pathogens shared by the global South.

Interestingly, both proponents and opponents of solidarity in this debate often fall into a common trap of focusing primarily on Responsive solidarity. In doing so, the proponents of Responsive solidarity, by focusing on the adversarial conceptualizations, tend to alienate the very actors they are trying to change. In other words, one could say they practice forms of un-solidarity towards these actors.Footnote ⁵⁴ The opponents of solidarity in this debate view invocations of solidarity as a threat to liberal ideas that are often at the very core of their existence. This was seen, for example, in the negotiations that led to the Pandemic Agreement, where the binding obligation of solidarity was increasingly weakened in the iterations of the document even though it survived in at least three places in the final version.Footnote ⁵⁵ The common trap into which both proponents and opponents of solidarity here fall, in our view, is an over-reliance on the current Euro-American conceptualization of solidarity, which eclipses a larger focus on Deep solidarity.

What would be useful here is a revisitation and clear inclusion of the notion of Deep solidarity. By relying on relational ontology, Deep solidarity underlines the fact that health, especially in today’s interdependent and interrelated world, cannot be adequately addressed by thinking only within national borders, or thinking only of corporate interests and profiteering. Diseases and health threats do not respect national boundaries; therefore, impoverishing substantive parts of the world by denying them access to health is harmful to the human community as a whole. Furthermore, climate-related health threats cannot be addressed without commitments to international cooperation. It is against this background of considerations of our shared humanity and collective destinies that commitments to global health that may require some abridgement of self-centred or parochial interests make sense.

Just as we saw in the African tradition, Deep solidarity embodies concern for the well-being of all and makes it a central issue of morality to act in ways that can be described as pro-social. Translating this into global health, Deep solidarity implies that to act morally is to act in ways that promote the health of humanity and not just those living within the confines of one’s state or in the interests of one’s corporate stakeholders.

4. Summarising the key ideas

This paper has argued that solidarity remains one of the most important, yet conceptually unsettled ideas in global health ethics and governance. Although solidarity is now routinely invoked during public health emergencies and international negotiations, its normative content is often left vague, which helps explain the persistent gap between rhetorical commitment and practical equity. The negotiation of the Pathogen Access and Benefit Sharing sections of the Pandemic Agreement made this problem especially clear. States endorsed solidarity in principle in the Pandemic Agreement, but they did so from divergent conceptual positions: some treated it as a binding commitment to redistribution, access, and shared responsibility, while others understood it as a voluntary and politically constrained aspiration. That divergence is not merely semantic. It reflects a deeper disagreement about what solidarity is, what it requires, and what kind of institutional arrangements it can justify.

Section 2 showed that the Euro-American tradition offers no single, stable account of solidarity. Its meaning has shifted from the Roman legal idea of obligatio in solidum, through nineteenth-century French theories of social debt and redistribution, to twentieth-century accounts of political resistance, collective action, and social critique. Across these transformations, solidarity increasingly came to denote a response to injustice, oppression, or crisis. Yet this historical expansion also produced conceptual indeterminacy. The broader solidarity becomes, the less clear its content and obligations are. In this tradition, solidarity is most often understood as Responsive solidarity: a form of action that arises in response to perceived harm, exclusion, or emergency. This model remains important, but it is limited by its reactive and often adversarial character.

Section 3 introduced a different orientation drawn from African philosophical traditions. Here, solidarity is not primarily a reactive moral stance but a constitutive feature of social life. On this view, persons are not isolated individuals who later choose relations; they are relational beings whose moral identity is formed through relationships. This yields what we call Deep solidarity. Deep solidarity is grounded in relational ontology and in the idea that moral life is structured by prior bonds of interdependence, mutual recognition, and shared flourishing. It is therefore not episodic or exceptional, but ordinary and foundational. In this framework, solidarity is not only what communities do in times of crisis; it is part of what communities are. This also gives solidarity greater normative depth, because it links obligations to the conditions that make human flourishing possible in the first place.

The final section brought these two accounts into dialogue and showed why the distinction matters for global health. The paper’s central contribution is to argue that Responsive solidarity cannot be effective unless it is supported by Deep solidarity. Crisis-driven appeals to solidarity are too fragile when they are not embedded in durable norms, institutions, and practices that recognize interdependence before emergencies occur. In global health, this means moving beyond the logic of temporary aid, exceptional generosity, or narrow national interests. It requires designing governance arrangements that treat states, institutions, and communities as partners in a shared health project. It also requires rethinking the donor-recipient framework, which obscures mutual dependence and reproduces hierarchical relations, and reconfiguring the epistemic economy of global health so that knowledge, health tools, and benefit-sharing are governed more equitably.

The paper therefore proposes a new way of thinking about solidarity in global health: not as a purely rhetorical ideal, nor as a thin universal principle detached from social life, but as a layered moral and institutional framework. Responsive solidarity names the urgent political and ethical work of responding to injustice. Deep solidarity names the prior relational and normative conditions that make such response durable, legitimate, and effective. Taken together, these concepts allow solidarity to be understood not as an abstract appeal to goodwill, but as a governing principle for collective life in an interdependent world.

Its broader significance lies in showing that global health justice cannot be secured through emergency rhetoric alone. If solidarity is to have real institutional force, it must be rooted in deeper commitments to relationality, equity, and shared responsibility. That is the paper’s central intervention- it reorients solidarity from a crisis language towards a more foundational account of global health governance, one capable of sustaining justice both in ordinary times and in moments of rupture.